To add something actually relevant to this thread, since we have no clue if or when 5870 mac drivers will exist, there is some very good news in its announcement:
The Eyefinity card with 6 mini-Displayports. If you hate MDP this is bad news, but for those of us who have to live with it, this is great news because it means it's becoming standard on hardware - that card only has MDP and is designed to run 6 monitors simultaneously. So it's now being built into cards and monitors, which means it is not 's niche product, but soon to be included standard on hardware that is not made by . I have to imagine that Samsung array they're showing it off on will use MDP if it doesn't already.