A surprising number of titles seem to support crossfire in VR, and it's much much more consistant then SLI was, and much, much better then hoping for crossfire support on a particular flatland game.
So far: literally everything in Unity 5.4+ . Everything made in Unreal 4+ as well, made with any version in the last 6 months.
Everything source 2, everything, becuase it utilizes per eye rendering. This includes Valve Destinations, etc, robot repair, dota2.
I've never enjoyed VR as much as I have tonight. Literally ZERO judder in New Retro Arcade: Neon at 2.0 supersampling and max resolution, with reprojection turned off, if that answers your question.
I would venture a bet that the performance of dual 480's for the purposes of vr is beyond that of a single 1080 unless the title supports single pass stereo (and I don't know of any that do)