Ryan at PC Perspective has just posted a review of the Asus A8R-MVP Crossfire Edition motherboard. Based upon the ATI Xpress 200 Crossfire Edition chipset, it should be interesting to see how Asus faired in dealing with an ATI chipset. Granted, ATI has had some growing pains initially in the chipset market, though their latest efforts seem to be gathering praise everywhere you look.
The A8R-MVP isn't available at any online stores yet that I could see and so retail pricing is up in the air. The best guess that I have based on Asus' estimates is that you should be able to find the board for about $125, much lower than the $200 that the DFI RDX200 is going for. If this is how things turn out, I can't see anyone paying $75 more for a board that uses the SB450 south bridge and doesn't offer SATA-II though the RDX200 does have some interesting features of its own. I'll update this conclusion page once I get more solid pricing information.
The Asus A8R-MVP is among the first ATI CrossFire motherboards to hit the market. With solid performance, features and a low cost this board should definitely be on your list if CrossFire peaks your interest.