Actually, there are no sub-races implemented in the game (nor where they available on BG2).
You get all the class kits that were on BG2; the 3 new NPC, the wild mage, the blackguard and the monk; the additional adventure (The Black Pits), tons of bug fixes (they claim 400+, although the game still has some bugs).
They also have some additional encounters, treasure, quests, etc.
You have a very cool zoom function, multi-platform multiplayer, near 0 seconds loading and saving times and probably some more things I might be missing.
All in all, a pretty good deal if you didn't own the original game. IF you had the original, then the 20$ price tag might not be worth it.