Seriously the only thing that really bugs me is the speed, or lack thereof. Most of the time when you think your phone is "freaking out" or "bugging out", it's just that it's so slow you have to wait on it to do something, so you get impatient and tell it to do something else, then it doesn't respond, so you hit the home button, then all these commands pile up, the phone goes nuts, apps force close, and you end up having to reboot. The Eris is doing something the whole time trying to keep up, but you can't tell. I partially blame Android just because it's so young, but most of it is the speed of the Eris. If the Eris was faster, it would respond faster, you would demand less of it, and things would go a lot more smoothly. If you take the EXACT same operating system and put it on two different phones (one fast and one slow), it doesn't matter how buggy the OS really is, it would seem less buggy on the fast phone just because it's doing what you tell it to do. At least that's my experience, but again I haven't seen too many real bugs, just hiccups due to speed and response.
For example yesterday I had navigation going and I tried to call someone. It was a serious royal pain. I ended up accidentally hanging up on the guy and the navigation came to a crawl. It literally took like a minute for the phone to catch up to what I was telling it to do. It didn't ever do anything wrong, it just took forever. On the Incredible it would have all been nearly instant.