Aw, I liked Taylor (in season 4). She and Ryan were sweet together, and Ryan having to deal with her neuroses was a nice step up from all of Marissa's problems, and she brought a lightness to Ryan when he really needed it. She's very Paris Gellar, but a kinder, caring (admittedly less funny) Paris Gellar.
I just watched the finale, which is a really great hour of television. I love the way the fourth season cements the Cohen-Atwood-Cooper-Robertson family. I think they used Marissa's death to bring the other characters together and create new stories in a way they couldn't have had she lived. It added a lot of depth for Ryan, Summer and Julie. Ryan and Julie worry about what the other will go through if Julie and Frank become a couple. She tried to frame him for attempted murder and sent him on a crazy revenge murder mission and he still thinks she deserves better than Frank Atwood. She finally admits she's put that kid through enough and can't do anything else to hurt him.
There's other bits of character development I really like about season four, like Seth becoming less selfish and helping Ryan come back to the family, making sure he doesn't kill Volchok, and rescuing him in "Night Moves" (stupidity that made the situation worse aside). Then he tells Summer she needs to go save the world and trusts in their relationship to last through it. Julie decides to get her degree instead of depending on yet another marriage for support, with Bullit and Frank still cheering her on on graduation day.
The family tree on The OC rivals the one from Once Upon a Time, but by the finale they have all formed this strange, beautiful, supportive blended family that all began because Sandy brought Ryan home.
Plus, I never realized that Jeff from Chuck was the weird homeless guy Seth gives the Range Rover to. Josh Schwartz must just love that actor.