I'm in the "they're perfect" camp
really, I do love them so much.
If I had to find something bad about the breed I would probably say: They are attention whores. Now this can be a good or bad thing, depending on you. I have one Yorkie mix and one pure Yorkie - but both insist on being with me 24/7. I personally love this, I couldn't live without my babies with me all the time, but I have some friends who couldn't imagine having a dog like that.
Good luck!