Any successful mecanum-wheeled (strafing) bots?

For those of you who don't know, mecanum wheels allow robots to strafe side to side in addition to normal control. Video: https://www.youtube.com/watch?v=O7FbDy-gE70

I'm interested in building a beetleweight robot that would implement this into a flame-thrower bot. This seems like a good idea in theory since the robot would control like a first person shooter. Using these wheels would result in a great loss of pushing power and traction, but the strategy would be to out maneuver and blast the opponent without making contact.

After watching a few videos on both mecanum and omni-directional wheels, one thing I've noticed is that they're all horribly slow. Do they require a lot of torque? Or are they just not building the bots for speed?

Either way, I'd like to know what you guys think of mecanum/omidirecitonal wheels and if they can serve a valid role in combat robotics.