The Vampire Diaries started out as a pretty generic teen vampire show, but after a few episodes it started to get more interesting. The characters and the stories gained more depth and suddenly this show turned out pretty addictive watching.
I just watched the season finale, and OMG, can't wait to see Season 2 :).
I was waiting for Katherine to appear, so when "Elena" started kissing Damon, I knew Katherine was back. And the end when she killed Uncle John was just AWESOME.
I'm sure it's going to lead into some delightful Damon angst next season, since whatever he says, he does love both Katherine and Elena. He tolerated Elena in the beginning, because she looked like Katherine, but later on they became unwilling allies due to her relationship with Stefan. But they did continue to become friends with time - and I don't think Damon even recognized he was also falling in love with her in the process, since he was so concentrated on Katherine.
He is my favourite character, despite being completely unrepentantly amoral. He has the best one-liners and snarky comments. His character seems quite complex based on all the back story and his actions, much more so than his brother.
There are lots and lots of interesting side characters whose stories also add to this series. At the moment I'm also worrying about Elena's brother after Anna was killer - will he die/turn or not and about Matt, Caroline, Alaric, and various other people that have been introduced in this series.
One other reason to like this series is the friendships. Elena and Bonnie are best friends, but as both learn new things, have new secrets, have new relationships, they learn that friendships doesn't always account for everything. They have their differences about matters and also different agendas at times, but they talk things through with each other. They also understand/forgive that the other might have a bit different viewpoint to a particular matter (like the vampires). To a point, at least.
The love-hate relationship between Stefan and Damon is interesting. They both loved Katherine (a dead ringer for Elena), who turned them both. Some flashbacks later on give more details about the story, which turns a lot more complex the later the season gets.
I had a strong suspicion Anna would die, especially after Pearl got it. They did need to kill at least one of the featured characters and her death would provide some delicious angst for Elena's brother who might or might not turn into a vampire in retaliation.
Random: I'm glad V got renewed, because there was no way they could have resolved all the stories by the end of this season.