I know that absolutely nobody ever seems to read my posts, but why the hell do you benchmark a multi-GPU system in MEDIUM DETAILS?!??!
I wrote a post about the MultiGPU Crysis patch and my benchmark findings in this Beyond3D post: http://forum.beyond3d.com/showpost.php?p=1116612&postcount=19
Cliff notes:
If you actually play with settings that you'd expect to use in a multi-GPU system, the increase is quite good. If you play on a 15" screen at medium details, you don't freakin' need multiple GPU's in the first place.
The point of that article was just to show if there were any improvements across the board (heh, excuse the pun ). The article was comparing Crysis pre- and post-patch, so it's useful just to know for the people out there. You'll note that on the last page, they finally do show a hefty improvement with the patch and crossfire in particular showed the most gain (DX10, HQ, 1920x1200).
http://www.techspot.com/article/83-crysis-patch-performance-multigpu/page5.html