Last year, my team (1293, D5robotics) used the 8" mecanum wheels from AM along with 4 BB transmissions, one for each CIM. Mechanically the bot worked fine last year, but we had some very very strange coding issues with the accellerometer that caused the robot to be highly uncontrollable at Palmetto.
http://d5robotics.org/Content/View.php?id=550
That is a video of our bot during build season, that is the first night we had it running. Here is an inventor rendering of the bot....
http://d5robotics.org/Content/View.php?id=548
We had no issues with the single CIM banebot planetary transmissions, we found them to be delightful (moreso than the dual CIM BB gearboxes, which shattered on us at Palmetto in 07, but that could be attributed to the fact that they were in the front of the bot, unprotected, and took a direct hit as we plowed into another bot at full speed)
The "white" chassis is made from UHMW, a nice and flexible plastic but very strong. We took a 1 1/4" (I think) sheet of it and water jetted the chassis from it. It offered a kind of makeshift suspension system that is vital with mecanum drives. It kept all the wheels on the ground since it was able to flex and absorb the vibrations caused by the wheels. The chassis UHMW costs 200 dollars for a slab that large.
8752K518 is the mcmaster product number