I've been using vanilla Android for almost a year now. The more I use it the more I dislike it. By far my number one complaint is bugs. Some of them are so apparent and easily reproducible is simply inexcusable that they're still there (all reported btw). I haven't rooted my Nexus One, so I don't have that to blame either.

It gets tiring to click the same message-contact shortcut and sometimes to be taken to the right place and sometimes to the list of users, or trying to attach an image and not be sure if the gallery application will crash or not (and having to manually close it), or after N text messages sent and getting a lovely "Message could not be sent" error not knowing if it's the messaging app misbehaving or my carrier (almost always a force close of the messaging application fixes the issue), or the scrolling in the browser acting up while locking and unlocking the screen miraculously fixes it... There's also the focus on fancy features like navigation while neglecting the basics like the phone part. I had more control / features on the phone side with my ancient Sony Ericsson dumb phone than on my "superphone"

The potential is there though...