The VSTi implementation (concerning tempo compatability) gets #1 here too.

A personal one is the flashing yellow warning messages could be shorter. Maybe longer the first time they flash, but shorter from then on? Sometimes I am done with the edit before it's done flashing. Something like the fade out takes a few seconds but the flashing lasts 10 seconds or so (it seems)
As a side note I do appreciate the newer 'edit-audio effects' shortcut in the right-click menu of the audio edit screen; and when used from that screen there is no flashing message (yay!)
I hope I didn't point out something you will now change ...

Having "The ability to loop through the same passage recording many takes that can be merged/edited into one "best" version" (as mentioned by OP) would be pretty cool also, if each loop recorded to a new track. I could see that taxing some systems, but for the ones that can handle it, it would be nice.

Also, at start up, if I don't have the external drive hooked up (that has the realtracks on it) when I start the program I have to dance through 3 windows (a couple "are you sure" windows)
How about a "Do you want to set up realtracks?" window instead of the current popup that attempts to set them up?
Then if I click "no" I don't have to go through the next few windows (vouching for my decision), and if I do want to set them up I can click "yes" and get to the setup window that is currently the first popup?

Not sure how many this would be beneficial to, maybe only me, but I often record, mix and do mastering work in RB without needing the external (realtracks) drive running.

I do not work here, but the benefits are still awesome
Make your sound your own!