We have yet to buy our second cRio. We have no regrets ...
VEX has worked very well for testing our robots and writing quick code.
Here is the KitBot VEX code we constructed in week 1 of FIRST
VIDEO VEX-KitBot testing:
http://www.youtube.com/user/lamardis.../4/OTfv0W_ymvQ
CODE:
http://code.google.com/p/discobots/s...20Vex%20Code.c
As for using an Arduino, I think its a low-cost alternative but the limited number of PWM and encoder inputs are not suitable to scale for a encoders on a KitBot