I meant to write this sooner, but....
I listened to all seven tracks from the ZELDA TWILIGHT PRINCESS OFFICIAL SOUNDTRACK, via MP3s off http://www.thehylia.com/, and I was quite pleased with what I heard. Here's an analysis of each track.
1. Orchestra Piece #2--I don't know if this is an alternate piece for the trailer or if it takes place somewhere else in the game, but it starts and finishes in the same style as that former track. After a fanfare and a quiet yet somewhat mysterious interlude, the piece explodes into a rousing, epic piece of music, complete with full instruments and a choir. The sound quality on this track is incredible--they really DID record an actual orchestra for this track. Kudos.
All the rest of the tracks are MIDI.
2. Hyrule Field Main Theme--As with Ocarina of Time, this is an all new "Overworld" with small hints of both the original Overworld and OoT's. It's more mature-sounding than either of those two, both in tone and composition, but it definitely has that "Overworld"-ish quality to it. There is also somber moment where we hear a synthesized male's chorus "aah"-ing while the remaining instruments continue to play. It took me a while to get used to this track; I was expecting something along the lines of what the first version of this was (I can't remember the link, Kenny might know it, though), but before long it clicked with me. The sound samples, BTW, sound really good--not on par with Paper Mario: The Thousand Year Door or Fire Emblem, perhaps, but still well done. Of course, this track--and all the others--are all enhanced with reverb, sort of as to give the feel that they are studio-mastered.
3. Ordon Village--This is, I think, the first place in the game. Nothing outstanding, but it's pretty much what you'd expect for a village tune: calm in nature and genuinely pleasant. The first part of the track involves pizzicato strings (which open the song) serving as a "backdrop" for what sounds like a panpipe. Later we hear woodwind and string instruments. Not one of the more outstanding tracks, but it serves its purpose and is fitting with the game's location.
4. Kakariko Village--Ironically, the only thing about this famous ALLTP pieces I identified were the opening six notes (played on what sounds like a high-pitched whistle). The rest of it is basically mellow, with light percussion and woodwinds. I'm sure the song is like this for a reason though. I'll know when I play the game.
5. Death Mountain--This is, I think, one of the most bizarre tracks on the album. Not in an offbeat, wacky way as in, say, Majora's Mask or WindWaker, however. It's the "Goron City" theme--with additional instruments: percussion, brass, and woodwinds. Having been so used to how the original sounding, hearing this new version was a bit surprising.
6. Midna's Theme--One of my favorite tracks on the album, outside of the first two: melancholy and mysterious in tone, and complimented well by somber-sounding strings as well as a oboe [clarinet?] solo. Too bad it's short, though.
7. Ilia's Theme--This is the only track where the datedness of the MIDI becomes apparent: The central melody--played what sounds like a cross in between an ocarina or a pipe--sounds fine, but the accompanying instrument sounds like one of those cheap vibe sound samples on an old Casio keyboard. That aside, this, too, is a short "new character" theme. It's pretty and pleasant, if not particularly rousing.
All in all, I wouldn't bother purchasing the NP CD just for these seven tracks--downloading them may be preferable; that way you don't waste any money. What's there, though, sounds very nice and I am personally looking forward to hear more than what I've already listened to from the game videos on the web.