There has to be some nasty security vulnerabilities lurking on that phone. There have been a lot of security patches to Android over the past 2.5 years to fix various exploits. I'm sure it does run great, but I would personally be uncomfortable missing out on so many security fixes.

I don't pay a lot of attention to the Android OS, but I do recall there was a nasty exploit discovered about a year ago (called Stagefright) where a specially-crafted text message with a picture or image can cause malicious code to be run on the phone the moment the phone receives the message.