James Marsters has been in quite a few things since then too, I think. He did a few episodes of Warehouse 13 (alongside Anthony Stewart Head, actually), and was brilliant in them. He's really excellent at getting the balance between comedy and serious just right.
Loved the musical episode. Spike singing 'Let Me Rest In Peace'... Yeah, hot.
Agree that season 5 was probably the best one, the season opener with Dracula was fantastic. And The Body was so sad but beautiful. And then Spike in the last episode when Buffy is fighting Glory, I properly sobbed watching that. Actually the first few episodes of S6 are excellent too, but it seemed to go off the rails a bit halfway through the season.