I find myself both loving the OST and feeling a tad miffed at it.
First, yes, the selection of tracks is astounding to say the least. I was surprised by some really weird but very pleasing song selections. I am LOVING the Mario remixes in this game. In my opinion, I think they are the best in the whole soundtrack, and the ones filled with the most imagination.
If you don't like ANY of the songs in the soundtrack then either your standards are set way too high or don't get a kick out of game soundtracks.
On the other hand, when compared to the Melee soundtracks the songs feel like they are missing something. They lack the heart and bounce the Melee OST had and thus may be more forgettable in the long run (save for a few clever remixes here and there).
Overall, though, it is a delightful soundtrack and thanks to My Music you can pretty much select what you want to hear and turn off the stinkers.