I'd say that the first 7-8 episodes are pretty strong for the most part (discounting 'Beneath You' & 'Never Leave Me') and the reveal of The First is well executed because the clues are all there from the very 'first' episode. Most of the problems with the season only really begin with the arrival of the Potentials.
Dawn's development is a huge step up from the previous season; she's funnier, sassier, more useful and accepted as part of the group as a result, we get to see her on her own in the new high school setting a few times, but not really enough. Also 'Potential' has some great Dawn moments and is a strong episode for her.
In theory I like that many of the episodes are dealing with various aspects of the Big Bad threat (its part of what I like about Angel S4) from the Turok-Han to training, to dealing with the seal-thingy to Buffy going to the Shadow Men for help, etc, but it all ends up feeling very same-y and half the time the character decisions seem stupid/contrived.
I think that's because ultimately the characters are not driving the plot, they are more often reacting to it and not really uncovering any information. In AtS 4 the balance it better handled as the mystery keeps unfolding.
Faith and Caleb's arrivals are a massive shot in the arm the end of the season needs and the pacing/sense of threat goes from turgid to urgent. From that standpoint the last few episodes feel much more dynamic than the middle ones. Plus its nice to see Faith play off characters in new and interesting ways.
Xander's quiet, behind the scenes involvement and support is well handled.
End Of Days & Chosen are strong episodes with a nice balance of character moments and looming apocalypse. And the end battle is pretty stirring and epic.
Riley getting one of his guys to refer to Spike as assface even as he helps Buffy; that was funny.
That's all I can remeber from memory but I'm starting a re-watch soon, so who knows what I'll (re)discover.
