116 basically had the design you are talking about last year. Thing is, it definately cannot climb. It's not because of slippage, but rather that the drive wheels will lose contact with the floor once your robot becomes inclined.
http://invisiblerobot.com/robotics/r.../p1060294.html
For example:
Pretend your driving your "north corner" (or face depending on where you mount the wheels, it doesnt matter for the purposes of this occurance) first. Once it hits the ramp, it will be pushed upwards, but the south corner, not having hit the ramp yet, will still be on the ground. The robot as a whole now has a few degree tilt on it. Because of the tilt, the east and west corners are slightly lifted off the ground, and after you drive a bit more, will completly lose any contact with it. Unless your robot is perfectly balanced, the robot will now tip twoards either the east or west corner, returning that corner to contact with the floor, but removing the other corner further from it. With the absense of this corner, you cannot drive straight forwards anymore.
Our holonomic drive even expierienced the beginnings of this problem with the mere climbing of the triangular loading zones last year.