Saw it last night, and it was pretty darn good. As a fan of the original book, I'm pleased with roughly 90% of the additions to the film series.
What bugged me a bit, though, was Legolas. I expected him to have a cameo appearance, possibly with a single sweet fight scene. Instead, he's one of the main characters in this film, with easily the best action scenes, which takes away a bit from the main plot. Also, they could have done a better job with his makeup. Orlando Bloom is still has his youthful good looks, but it's quite obvious that he's a decade older here than he was in LotR, in contrast with Hugo Weaving who looked just as timeless in Unexpected Journey as he did in the original trilogy.