Adding my RC2 comments to this thread
Projects saved in M8 2.0 don't "just work".
I had a project using 1080p footage saved in 2.0. Open in 3.0 and the sizes are wrong, so I use the Project Settings and set the project to 1080p. But now the *positions* are wrong, because positions are saved using pixels, and where -240 used to center something on the top edge of the screen it now equates to slightly above center.
I'm not sure what the best approach is now... arguably X and Y positions should have been scaled to 1.0 from the beginning (although with different aspect ratios it is hard to say exactly what 1.0 would have meant) Now everyone's projects (and modules!) have the legacy 640x480 scale baked into them, and any project you want to use in 3.0 is going to require auditing and possibly repair.
Maybe the x and y values should be internally scaled to make -240 always correspond with the top of the screen? Or, should I (or everyone) keep the stage 480 and only adjust the width to get the correct aspect ratio? (it'll still render every pixel of fully scaled 1080p footage outputting to 1080p screen, even if the stage is 854x480, right?) Can you refer to the 2.0 preference / output settings to automatically set the project settings to guarantee that the same content to the same display will be pixel-for-pixel identical when opened in 3.0?
The new stage and scaling options seem nice, but it is a really big problem if you can't guarantee that a 2.x project will open in 3.0 and "just work". I have probably over 100 .md8 files (often one for each song of an artist I work with) and having to fix every single one is a huge barrier. IMO you need to think hard about how to make this work smoothly.