Went to the midnight show last night as well. Wow, there's so much that's good about the movie that its difficult to sum it all up. Everyone's mentioned the highlights of spectacle that happen, so let me just add how great some of the more subtle touches are -
Gollem has taken yet another leap forward in realism. There's scenes with him and Frodo on long, holding close-ups of the two of them in the same frame. The CG performance is so good, you forget that its an animated character at all.
This time around Peter Jackson has pulled off classic horror-style suspense with the Shelob sequence. It feels fresh and tense but with a classic feel to it. I thought it was a great touch and a good wink to his roots.
Then there's the battles. The glorious battles.
It's not ALL good, however.
It's probably because we've been conditioned to the EE's on DVD, but you feel the absense of material that will obviously be restored next year for home video. Even at 3h20min it feels short!
The absense of resolution for Saruman is brushed off with a Lucas-flimsy dismissal. We know the sequence is returning on the DVD, but considering the time afforded at the end for all the other characters to wrap-up, you're left wanting.
Also, as well as the Sam/Frodo relationship develops in the movie, the dialog runs out of gas long before their actions do. As a result, expect a lot of 'Mr. Frodo!' 'Oh, Sam' remarks and longing, loving glances that, well... push the boundaries of male bonding.
These are, of course, minor hiccups in an otherwise fantastic movie. Worth seeing again, me thinks!