Finally! The soundtrack has been uploaded somewhere. I've listened to most of it, and while it's good, I couldn't put it above the ones from the first two games (which I like about equally). Seems Koshiro wanted to break from the mold a little with this.
My favorite tracks from the previous games tended to be the soothing stratum themes, but they're a lot more upbeat and/or experimental this time around. The first stratum track is easily the most traditional, but it changes almost completely from there. Second one conveys a water level type of atmosphere and sounds unlike anything else. Third and fourth are a lot more upbeat...the fourth sounded pretty good for what it is, but I'm kind of indifferent toward the third one. Fifth is the awesome track they used in one of the last trailers; it's got a traditional-sounding composition but is more upbeat. Hard for me to describe the sixth stratum's song, but it's pretty interesting. Couldn't say anything beats Petal Bridge from EO2.
I think the battle themes are, in general, the weakest in the series, but it's not like they're horrible or anything. On the contrary, this game by far has the best 6th stratum battle theme.

Anyways, perhaps I'll warm up to the soundtrack when I can finally play the game. I remember there being a few tracks that I thought were kind of "eh" in EO2, but they clicked when I got around to playing it (especially the second stratum's tune and first battle theme).