In reply to Sally G.

The feature works pretty well, and even the customizer aspect of it is better than what I thought it'd be. At a certain point, you just need to put software into the hands of users and iterate based on their feedback. Otherwise, you're just building within a bubble of like-minded developers. The biggest known issues (like the theme issues) were always known, and they're going to come down to theme authors addressing them on a case-by-case basis.

Personally, I plan to mostly skip over block widgets and start moving toward full block themes with "block areas" instead of sidebars/widgets, at least on projects where I can.