Funny you should ask; I just saw a mid-weight team riding a Cannondale RT2000 with a pair of blue-spoked Rev-X's at Southwest Tandem Rally. That said, here's what Spinergy has previously stated:
Can rev-X or rev-X-roks wheels be used on a tandem?
NO. Although the Rev-X design is exceptionally strong, the forces exerted on a wheel used on a tandem are much more significant. Tests of these forces have not been done yet, so the use of the wheels on a tandem voids your warranty.
I believe this falls into the realm of "you're on your own if you do". While they would probably work OK for a while, I'd be surprised if they'd prove to be durable enough over the long haul for anything other than special event wheels, e.g., time trials, etc... It's kinda like the team we saw running Zipp 909's; they are strong enough for Time Trials on an infrequent basis but once you heat them up with heavy-duty braking they delaminate and are worthless. Apparently, the expense was not a major issue for this team, or so we were led to believe, as they purportedly have gone through several sets on 1/2 bikes and the tandem (Yikes!!)
Personally, I'm still not convinced that conventional component wheels are measureably less efficient than the highly-touted paired spoke (Shimano/Santana, Rolf or Bontrager) or other chi-chi integrated wheelsets and certainly more durable and serviceable. After all, so long as these wheelsets use rim brakes, rims will forever be components that need to be replaced. Now, if you buy-in to integrated wheel systems you'll most likely be dependent on the manufacturer (or their suppliers) to provide you with the rims and sometimes even the spokes to keep those wheels rolling. However, with a good hub like a Phil Wood, Chris King, or White Ind., model you're pretty much a free-agent who can switch rims and spokes as you please.
Just something to think about....