Personally, I buy nVidia early in the life cycle of any series because I've found driver support to come quicker and be more complete. And I'm willing to pay for that.
Later in the life cycle, ATI has caught up and the price performance improvement is now worth the few $ saved.
So if you were buying today, I'd recommend a *single* ATI card that will satisfy your requirements for whatever SCREEN RESOLUTION you are using. That way, one year later or so, I'd have a choice of buying a different single vid card, or a (now cheaper) second card for crossfire. And because SLI/Crossfire have both historically shown they do not help in all games.
If I were to wait . . . having seen *nothing* definitive (ie objective, trusted reviews) of "5-series" or "3-series" cards . . . I'd probably lean toward nVidia as stated above.
Message edited by Twoboxer on 08-27-2009 at 02:07:56 AM