We bought three last year in addition to the one we got for free. And we already had two from a summer high school robotics camp that WPI had (we were actually a "testing platform" for the EDUbots).
So why did we need so many? Well, for the annual "miniFIRST" competition -- aka The Intergalactic Savage Soccer Competition.
http://www.massacademy.org/minifirst
In the past we had used R/C car chassis and allowed the students to build stuff on top of that which was battery powered, but that's it really. We decided last year to make a huge leap forward and use the EDUbots and it really was great. We made the playing field better, made a much more interactive game, used TacOps (our custom scoring software which was developed originally for BattleCry in place of using FIRST's) for field control and scoring, loud music, big screen complete with camera views and Flash overlays. Yea, so we went all out last year, and it was so great we may actually be inviting area teams to compete this year (it has traditionally been a MassAcademy-only competition).
I have a video that summarizes miniFIRST which I made for a class that one of our grad students was teaching, it shows the game and the robots and stuff
If you're interested in seeing it just let me know (through any means, email, IM, whatever) and I'll send it your way