The second half of Season 4 was phenomenal, with standouts like the "pictures" episode and Derek's final attempt at getting to Peyton. The Derek storyline acquires some unfortunate subtext once you know about Mark Schwahn, especially since it ends on a sympathetic note for Derek (!!), but what great, soapy entertainment. And, of course, the truth about Dan killing Keith finally comes out and it's as juicy and exciting as predicted.
Season 5 was predictably an adjustment. Not necessarily because they jumped ahead four years and the show became quite different as a result, but because starting over just comes with growing pains and a loss of the tension/momentum built up until then. Interestingly, the other major soap of the 2000s, Desperate Housewives, jumped ahead in Season 5 as well and its producers said the same thing: It's like doing a new pilot. Only thing is, if those Season 5 episode 1's were the first episodes I'd ever seen of either show, I may not have necessarily continued to watch. Their original pilots stood out much more. In any case, I didn't enjoy Season 5 as much as I remembered the first time around because its general vibe/tone was somewhat subdued/heavy, it came at the heels of excellent Seasons 3 and 4, and there was somewhat of a lack of those OMG! cliffhangers we had come to expect and love (again, due to things needing to rebuild/start over again). I still watched it in less than three days, though!
Nanny Carrie was a great story, looooved touching base with Tim/Bevin/Rachel etc., Skills and Deb getting together, Dan dying, and really enjoyed that Dan was left in prison for more than half of the season. Then again, Dan was in prison for more than half of the season, and considering the driving force for drama he is... Anyway, the whole thing ended in a great double cliffhanger (Dan hit by a car, Lucas making his choice--which is it?).
And, now, the first episode of Season 6 and it feels the show is back on track! The energy is just up. I remember the Carrie story clearer now and it's both fun and terrifying watching Dan get his karmic retribution. Peyton and Lucas finally back together, Mouth's touching goodbye, and that shocking ending of Brooke being attacked.... I've seen about one third of this season before but only remember some of the Carrie stuff, so it'll (hopefully) be a wild ride and I can't wait! After that, it's all new...