I think it really isn't too difficult to make it work, you can use one 2-axis joystick to move the robot in the 4 directions or diagonally, and another single axis joystick to rotate the robot. The one's we've played with here were done that way, this thread
http://www.chiefdelphi.com/forums/sh...ad.php?t=50030
has some information about it and a link to the code for a vex controller. Both of the mecanum robots used the vex controllers, not FRC, although the big one did use the big drive motors and Victor speed controllers. Our big one is shown here
http://www.chiefdelphi.com/forums/sh...ad.php?t=59027