This is actually my favorite season of all of Buffydom. By adding Spike the show became essentially a parade of Buffyverse Baddassery. With Spike, Angel and Wesley wandering around taking names it was like a fanservice explosion in my face.
I truly enjoyed the addition of Harmony and Spike when he's not desperately and whimperingly in love in Buffy is a true joy. I think the Spike/Angel friendship/hateship/brotherhood/sexual tension? is the best relationship in all the Buffyverse and to get an entire season about it... wheeeee! Not to mention Connor comes back with a personality that I can stand. Cordelia gets to come back and be herself again. Wesley is firmly entrenched as supreme buttkicker, Gunn becomes corrupt lawyer dude, even Fred is rockin the science to your face. Essentially the entire team took a level in Badarse and it was awesome.
The number of episodes in the season I consider superior, Hellbound, Lineage, Destiny, Harm's Way, Damage, You're Welcome, Smile Time, Hole in the World, Shells, Underneath, Origin, Time Bomb, Power Play, and Not Fade Away. I could have picked a top 10 list out of just this season.
Also I wouldn't be to upset about ALL the deaths, Joss has stated that had he been allowed a season 6 (which he expected because the rating for Angel had gone UP) he would not have killed Wesley, Fred would have started some time of time share with Illyrias body, and Gunn would have come back as a vampire Big Bad. Lindsay just needed to go he's a bad boy!
Anyhow, it's my favourite.