There's not really much of a difference between this and the original. Some tracks have different names, and the PAL versions are just slower. Overall a decent soundtrack, but there isn't any reason to download this soundtrack if you have the original.
I guess people see the name changes for some of the zones and think "Wow, some new music, I'll download it", when really it's exactly the same as the original. If you're looking for a good remix, check out the Sonic 2 Anniversary Edition. Now THAT'S some good music.