I could pontificate on how I felt about Gossip Girl, but Alessandra Stanley over and the NYT does it so much better.
I will add that despite the fact that very little of the plot is changed the show doesn't feel like the train wreck the books describe. It'll be interesting to see where they go from here, when they have to start making up completely new story lines, and which ones from the books they do include.
The discussion of the pilot is already ten pages long over at TWOP, but in general I think the audience digs it. Most seem to have not read the books. Maybe they will. That's an exciting thought. What else would you recommend to someone who loves the books/tv show?