I'd like to choose a category, but it's multiple at this point. The main ones...

• Bounding box randomly disappears. I turn it on. It randomly turns off.
• I select text and go to change factors and the changes affect other text that's not even selected.
• Photoshop completely changed the sizing to no longer require shift to preserve aspect ratio, which is unnecessary and fixing the things not broken, but if you're gonna do it in one app, do it in all. Kinda ridiculous to jump between programs and not have same functionality.
• If I go from dual monitors to single, canvas windows are somewhere off screen. This is on Photoshop too, and is eternally frustrating.

Illustrator is definitely the most buggy of all the Adobe software, and the bugs are just random, so no way to ensure I can reproduce, but always have to restart to get back to normal functionality. Lasts for about 20 minutes. This last version is buggier than the last, which begs to wonder who's testing and fixing bugs in the first place?