Great question, great responses.
For me, lack of time, lack of technical skill, and fear of loss of functionality / creating a new time-sink project that I can't afford right now kept me using what was working.
But just last weekend I got around to trying out Focal on my backup OP5 (with a half-melted screen) and it's largely going quite smoothly. I flashed without wiping data, and that process was pretty pain free. A little bit of messing around with settings, but all my messages and apps persisted, some apps just needed to be deleted and reinstalled (the appstore option to Install Stable Version didn't work, but delete then install is fine).
I really miss the Scaling of UT Tweak tool. The default 21 is way too big for me. It'd be amazing if/when that app comes along, for scaling and app suspension. Meanwhile, great to see some of those features entering System Settings!
Jitsi video calls are the other big thing that went from working to not working. On my Oneplus 5T 16.04, they work in both Morph and Jitsi Web App. On my broken Oneplus 5, 20.04 it crashes in both. Very similar phones. I presume it's a Focal thing, but can't say for sure. It does manage to get a hint of video out to the other caller before crashing. It's not essential for me, but a pretty nice option to have. Causes me hesitation in switching my working phone over just yet.
@Moem On my Oneplus 5, flashing through the installer without clicking the Wipe Data button didn't result in any lost files. But a GUI backup option would sure be great in any case. Hope your install goes smoothly
@MrT10001 Fantastic list of devices, and very useful comments about functionality. Thanks!
All those developers making apps work in Focal, thank you so, so much. I never stop appreciating how much this community does. Bravo!