I've had it for ages, but in the last week it's give me a **** load of problems and keeps telling me to upgrade flash player when I'm at the current version already. It seems to of been fixed though. Everything else about it seems fine.
It looks terrible and lacks greater function. In fact, it feels uglier and less intuitive to use than the old one. I hated it when they removed the skip to beginning button and I hate this now. I'm considering just ceasing all youtube activity over this.