Hello Roland.
First of all, I thank you much for so well working 1.5, it has helped me a lot in this hurry time; it's the editor which simply does the job well and I can work fast with. I started to think about a note "built with a help of LDCad" added to my builds labels at exhibitions
Finally, I had some time to test LDCad 1.6 and here I come with my observations and ideas.
The first difference to 1.5 I saw was that "+" hotkey no longer works in the partbin, "-" still works. After some testing I found what's the problem: on the US keyboard, "+" is a sign I can get only with Shift and new hotkey machinery is confused with that. Setting the hotkey to "Shift +" is a workaround but that would probably cause "+" on numeric keyboard stop working, if I had any. So there is no way to make them both working now, as it was in 1.5.
More about hotkeys:
* it does not warn me if hotkey is already assigned (and to what), it would be nice if a simple popup window appeared, with that warning and a choice what function I want to set this hotkey to (the old one or the new one)
* could you add "alt" to the list of modifiers?
* how can I assign a hotkey to (sub)menu? For example: Alt-F for "File" menu or Shift-Alt-S for View->Editing_views->Split (Yes, I want to hide menubar and have all menus accessible via hotkeys. I have really small screen on my laptop, especially vertically.)
ROTSTEP editing is great feature! The button "Sample view" confused me at first, maybe "Current view" would be more understandable, but it works well in both ways: getting the view and setting it. This makes my life with LPub much easier, thanks!
Group layers feature: technically, it works. And I remember I already needed something like this several times so I really support this idea. Unfortunately the current version is very hard to use and not intuitive. So the feature itself is great and works but, please, add new GUI for that. What about hiding all technical details about layers and simply provide a submenu with a list of currently defined groups, optionally with a name? That would be much easier to use!
MPD cleanup: works and works well. Thanks for it. There is finally a way how to delete flexible parts from the model
Unhide in the Source window: great feature, I like it. Unfortunately it's dangerous because the same hotkey is there for hiding and unhiding ("h") and I cannot even set them to different ones in the hotkey manager window. One of first things what happened during my testing was: I forgot I already have some hidden parts selected, their lines were out of the screen. Then I selected some visible parts and wanted to hide them. What was my surprise when another parts appeared instead!
For more reasons I believe it would be really useful if there was some visible indicator "you have something selected even it might be invisible or hard to see" - something similar to "I" icon in the bottom-right corner? For example I had some hidden parts selected, forgot about that and double-clicked on some part in the partbin. Those hidden parts were silently replaced with that part and, of course, I found that minutes and minutes later when I unhide them - and it was too late for any undo.
Mirroring feature: I did not test it much because it's probably more about missing parts metadata. What I can say is about GUI again: a selection of "X", "Y" or "Z" axis is a random shot, I really cannot remember which is which, it is not shown anywhere in GUI. If there was at least a color corresponding to the diagram of axes in the bottom-left corner, it would be easier. Better if it was shown "in place" instead of a separate popup window, something like grid is - another hotkeys for setting and showing the plane for mirroring.
Region select: great feature! Really helpful, I needed that so many times... Is there a way how to do rectangle unselect, too? The part about 3D box is very hard to use for me, I'd need a way how to see that box and rotate the view at the same time.
Random thought: what about stopping the LMB function of turning the view? I slightly remember you had this as a long-term goal (if I'm corect), it confuses me a little and it's not good for anything, RMB is here for that.
features not tested so far: BUFEXCHG, model reorganizing (embedding of unofficial parts, taking subfiles out of the file etc.), model header editing, scripting.
About scripting: one of my dreams is to make a script allowing user to select a rotation center of the part or group of parts to a specific snap point (resp. the axe of that snap object). So one can bend hinges, rotate 1xN plates on a stud, rotate Technic beams around axles etc. If you remember my video showing this. Would it be possible to work with snap points in scripts? And let the user to select it?
And maybe there would be a chance to add a function/script for making triangles. I know there is already a way how to do that with that helper you showed in one of your videos but it's too complicated and manual.
Oh. I can see how long post I created now. I hope I did not overfill the input buffer of your head Take it as a summary of all those missing posts during all that time I was silent 
First of all, I thank you much for so well working 1.5, it has helped me a lot in this hurry time; it's the editor which simply does the job well and I can work fast with. I started to think about a note "built with a help of LDCad" added to my builds labels at exhibitions
Finally, I had some time to test LDCad 1.6 and here I come with my observations and ideas.
The first difference to 1.5 I saw was that "+" hotkey no longer works in the partbin, "-" still works. After some testing I found what's the problem: on the US keyboard, "+" is a sign I can get only with Shift and new hotkey machinery is confused with that. Setting the hotkey to "Shift +" is a workaround but that would probably cause "+" on numeric keyboard stop working, if I had any. So there is no way to make them both working now, as it was in 1.5.
More about hotkeys:
* it does not warn me if hotkey is already assigned (and to what), it would be nice if a simple popup window appeared, with that warning and a choice what function I want to set this hotkey to (the old one or the new one)
* could you add "alt" to the list of modifiers?
* how can I assign a hotkey to (sub)menu? For example: Alt-F for "File" menu or Shift-Alt-S for View->Editing_views->Split (Yes, I want to hide menubar and have all menus accessible via hotkeys. I have really small screen on my laptop, especially vertically.)
ROTSTEP editing is great feature! The button "Sample view" confused me at first, maybe "Current view" would be more understandable, but it works well in both ways: getting the view and setting it. This makes my life with LPub much easier, thanks!
Group layers feature: technically, it works. And I remember I already needed something like this several times so I really support this idea. Unfortunately the current version is very hard to use and not intuitive. So the feature itself is great and works but, please, add new GUI for that. What about hiding all technical details about layers and simply provide a submenu with a list of currently defined groups, optionally with a name? That would be much easier to use!
MPD cleanup: works and works well. Thanks for it. There is finally a way how to delete flexible parts from the model
Unhide in the Source window: great feature, I like it. Unfortunately it's dangerous because the same hotkey is there for hiding and unhiding ("h") and I cannot even set them to different ones in the hotkey manager window. One of first things what happened during my testing was: I forgot I already have some hidden parts selected, their lines were out of the screen. Then I selected some visible parts and wanted to hide them. What was my surprise when another parts appeared instead!
For more reasons I believe it would be really useful if there was some visible indicator "you have something selected even it might be invisible or hard to see" - something similar to "I" icon in the bottom-right corner? For example I had some hidden parts selected, forgot about that and double-clicked on some part in the partbin. Those hidden parts were silently replaced with that part and, of course, I found that minutes and minutes later when I unhide them - and it was too late for any undo.
Mirroring feature: I did not test it much because it's probably more about missing parts metadata. What I can say is about GUI again: a selection of "X", "Y" or "Z" axis is a random shot, I really cannot remember which is which, it is not shown anywhere in GUI. If there was at least a color corresponding to the diagram of axes in the bottom-left corner, it would be easier. Better if it was shown "in place" instead of a separate popup window, something like grid is - another hotkeys for setting and showing the plane for mirroring.
Region select: great feature! Really helpful, I needed that so many times... Is there a way how to do rectangle unselect, too? The part about 3D box is very hard to use for me, I'd need a way how to see that box and rotate the view at the same time.
Random thought: what about stopping the LMB function of turning the view? I slightly remember you had this as a long-term goal (if I'm corect), it confuses me a little and it's not good for anything, RMB is here for that.
features not tested so far: BUFEXCHG, model reorganizing (embedding of unofficial parts, taking subfiles out of the file etc.), model header editing, scripting.
About scripting: one of my dreams is to make a script allowing user to select a rotation center of the part or group of parts to a specific snap point (resp. the axe of that snap object). So one can bend hinges, rotate 1xN plates on a stud, rotate Technic beams around axles etc. If you remember my video showing this. Would it be possible to work with snap points in scripts? And let the user to select it?
And maybe there would be a chance to add a function/script for making triangles. I know there is already a way how to do that with that helper you showed in one of your videos but it's too complicated and manual.
Oh. I can see how long post I created now. I hope I did not overfill the input buffer of your head
Take it as a summary of all those missing posts during all that time I was silent