My guess is that he's one of those people who don't really notice slightly clipped/sluggish animations. I know lots of people who see nothing wrong with their iPhone 4 animations when I can tell that they're jumpy as hell. It's all about perception. If you're the kind of person who notices little visual details, it may bother you. I don't think the OS will actually be "sluggish" in any meaningful sense, though. It's animations will look choppier. Which, IMO, is a big fail...but what can you do?