"S5 has an intriguing set up but so far feels a bit underwhelming especially since I heard a lot of good of the season. Haven't been enjoying Spike all that much (which isn't a big surprise since I hadn't liked him much in Buffy S7, one of the other reasons I didn't go through the hassle of catching up with AtS)."

I had mixed feelings about S5. I appreciate it was an attempt to take the show in a different direction and the premise is potentially interesting but the season story arc mostly wasn't all that compelling although there are some good episodes in there (particularly Smile Time). I think it might have been for the best that it was cancelled at the end of S6 since a sixth season would have lacked most of the characters I actually liked in the show, and the final episode was a fitting finale for the show.

I haven't seen the final season of Lost yet so can't comment on that. I'm currently wondering if I'll manage to avoid spoilers until I get to see it.