So, this is a shot in the dark. I have checked back every month or so for the last few years waiting for a new version, and so far disappointment. But I'm not developing it so I don't know what the troubles could be. I hope 5.0 will be worth the wait!
This is to list a bunch of features that would put you head and shoulders above the competition, and I would personally love them all.
-Non Planar Printing
Let's say I have a regular 3 axis 3D printer, and a special nozzle that is a bit more tapered on the end. I have a model that would have a slightly curved top, of course it would have its limits as far as curvature. But this way you could completely smooth the 'top layer', but that top layer would be not on a single plane. Would be awesome.
-5 Axis Printing
This sort of goes with the previous request. I have been experimenting with the equivalent of a C axis on my printer, essentially a stepper that moves a rotary table or chuck. I have been able to create some very interesting parts, specifically high pressure fittings because my alignment of filament layers can be perpendicular, there is no weak point where the layers connect. I would 100% build a 5 axis 3D printer if I had the software to easily control it. I have been looking into using a regular CAM program to get the toolpaths, then just modifying the program but this is long and arduous. Even more so for 5 axis since the amount of code generated is insane if it is simultaneous.
While I can already change my tool heads for different filament with regular G and M codes, what I can't do is change nozzle sizes for certain layers, then swap back to other nozzle sizes. This would be an amazing addition to say, print with a 2mm nozzle very fast for the walls, or any infill, then switch to a smaller nozzle when finer details are required. If I am printing a box with letters on the top, I could print 90% of the box, then the top layers with text could be with a .4 nozzle in order to retain small characters and detail.
Right now there is a way where you can offset your part at a certain angle, add supports, then reset it to the original position and have angled supports. It would be awesome if this feature was better supported, there are a lot of times I don't want my supports touching the rest of the print, but would like to have them come off of the bed. Also supports in general feel kinda crappy, unintuitive. Especially when manually placing them. I think that if the support models boundaries were better defined with maybe a black line or something it would help. It is sometimes hard to tell where the support ends and the model begins. Also for the manual supports, maybe render them as what they will actually look like and not just squares. Have the support settings in the manual support window, that way you can change on the fly and not have to place squares, then slice, to see what they look like, then go back, move it a little. It is just clunky.
If I think of the others I forgot I will edit the post. I hope everything is going good with development!