I like the idea of Drow being part of the game but I have found a few flaws that would arise from their implementation into the game....
First off it seems that there are already other playable races in the works namely dragons and dwarves (atleast from what i read in frequently asked questions thread) I would hate to see two many playable races pop into the game at one time and mess up all the balancing. I think back to when Death Knights were added to WoW, they were fun to use but really over powered in the begining. of course all new content needs tweaking eventually but Drow as of now seem to be a bit of a stretch.
Also Drow primarily live underground with doing surface raids very rarely. This would require the need for a whole new siege mechanic of attacking cave systems since thats where the Drow live. Also the Drow would have to have some sort of debuff applied to them when on the surface since they arent used to the sunlight. I also remember in the Forgotten Realm books that their magic was altered by being on the surface. These could turn into very cool game mechanics however.
I think if the Drow were added to the game in a seperate world with different mechanics suited for cave living that would work fine. The game could even go as far as to add Gnomes and Dwarves in the caves of the underdark for a whole new experience to the game.
odd thing is, as i wrote about why they shouldn't be in the game i ended up ratteling off features that seemed really cool to me >.<
(this is my first post... hope it was helpful)