Actually, being pedantic here, but the tune was composed by Ron Grainer. The original was arranged and performed by Delia Darbyshire. She also created the famous Woo-ooo-ooo noise by looping bits of tape and playing them at different speeds.
Edit: You can see all the title sequences upto and including David Tenant's at
http://www.youtube.com/watch?v=OuH4y3tbG0g
And yes, I did enjoy the episode. Unusually, the series hit the ground running, apart from some bad camera work.
Matt Smith: Could be a good Doctor. Came across as possibly being slightly creepy, which could be good.
Karen Gillen: Amy is nicely inquisitive . Seems like she could get herself into some interesting situations. Looks good as well. Actually, she seems very much like the young Sarah Jane Smith in this regard.. I've seen Karen in other stuff as well, and she is a good actress. Particularly good at accents (something which they took advantage of in this episode).
The new Tardis: Looks good. And they've already mentioned it has other rooms, so maybe we'll see a few. It always bugged me that in the RTD era, the Tardis only seemed to have one room, where as in classic who, they hinted that it had thousands of rooms. In fact, IIRC, Tom Baker (in The Keeper of Traken) mentions that he is jettisoning 1,000 rooms or 10% of the rooms in the Tardis.
As for the new theme tune, well, I don't insist that any Doctor who theme has the woo-oo-oo sound (I liked the Davison era theme and that didn't have it), but this theme seems like they had a lot of ideas for a theme, couldn't decide which one to use, so used all of them. Too much going on musically for my liking.