Well, yes and no… read on for details.
I ran into a couple of reviews you might be interested in. The first is FiringSquad.com’s review of Crossfire technology and the second is ExtremeTech’s comparison of SLI and Crossfire. Both articles provide benchmarks using some reference hardware supplied by ATI. Both articles come to the same conclusion… wait a while.
Though Crossfire will certainly improve your framerate when compared to a single ATI card, the performance isn’t that much better than a single 7800GTX. This isn’t surprising, since the X850 is a generation older than the 7800. It’s best to wait until you see what ATI’s new R5xx chips are capable of.
The first generation of Crossfire also has a limitation imposed on it by the single DVI channel that it uses to share video between the two cards. Though I’m certain that this won’t get in the way of most people, it’s bad news for anyone who wants to “future proof” their machine.
So… Too little? Well, we really won’t know until we see how the R5xx plays with Crossfire. Too late? Yep. About a year.
Update:
AnandTech has a list of recent Crossfire reviews that you can browse at your leisure. No sense reprinting them all here.