[JesseK]

The biggest lesson to learn about mecanum drive:

If your ability to score in the game is hindered, it's going to be a loooong tournament. Your manipulator, ramps, elevators, shooters, or whatever else better work well.

Also, mecanum wheels are pretty terrible at driving up inclines. The only reason a mecanum bot could drive up 1885's ramps last year was due to the side rails that kept other teams from sliding off sideways, and even then they had to gun it and pray.

Even with all of what everyone has said, it never hurts to get started. In CD-Media look for the white paper called "strafing.pdf". Mecanum drive is described in detail in there and it has the end results of a robot-centric motor output equations. Coming up with the control system will take the longest, so if you're interested in mecanum start with that and buy parts after Jan 5th if the game fits it.