What's more important would be a good cross compile for Raspberry Pi. By that I mean a 64-bit YABU install which has a script or something to setup cross compiling to Raspberry Pi.

Personally, I haven't used U++ yet. Been in the cross platform world since days of ZAF (Zinc Application Framework) on DOS. Most recent years spent doing Qt for embedded systems. Looking at U++ now like many others because current owners of Qt have started demanding licenses and royalties so they can adopt a lifestyle to which they would like to become accustomed. A serious number of embedded projects are now looking for alternatives, especially for projects starting some time next year. One thing which made Qt so popular was being fairly simple to set up remote debugging.

P.S. That one U++ to Qt comparison is from when Trolltech owned Qt eons ago.