I think Angel did alright, but yeah, Buffy really suffered for it. Season 6 was a depressing slog, but season 7 was a mess with a lot of cool ideas that didn't really feel like they got proper follow through. It promised to be a return to the more fun stories, but it fell back into old habits. Shame he couldn't wait one more year.
Anyhoo, still excited. The previews don't seem to have the strength of Whedon's humour, but I think it's just that out of context it doesn't work as well.