I really love the Google Maps widget! It keeps my wife in check when she's driving around town hunting for places to go.
However, when I was getting ready to get the iPhone and reading up on it, one of the features I thought to be least useful was the YouTube widget. I've always gotten on YouTube occasionally when someone would share a video with me, and I think it's a great site. But I never found myself using it too often. When I got my iPhone, I let my wife go out with her friends, and I found myself sitting on the couch with a beer for over 2 hours playing with YouTube. That crap is addicting.
Now if they would get cracking on converting all the videos to iPhone style!