Nothing flat out broke, but I am developing and dogfooding on a Mac, so I get visual QA for free on that platform. When I tested my app on a Windows machine, I noticed several UI regressions that looked/felt really janky. I didn't get as far as testing a Linux build, but I assume I'd find more issues there.
I can't remember why I wanted to migrate to 2.0 now, but there was a nice-to-have that I couldn't do in 1.4. I ended up abandoning the 2.0 migration after a slew of cryptic errors, took a step back, and decided I'd be better off using Electron for my project. My app is at heart a rich UI text editor and none of the computation is that expensive. With all the value add coming from the interface, optimizing for consistency there feels right.