What I can tell you about CAN from experience is, the Wizard (My team's robot) wouldn't be the same without CAN.
The current sensing abilities of the jaguar are invaluable.
- Before ship we used it to determine how much current was used going over the bump (70 amps per side!
and that was in low gear!). Because we were able to see that we were pulling way too much current, we ordered new sprockets to increase the torque output, and thus lower the current needed.
- In autonomous, we use the current sensing ability to good use in our ball magnet. The ball slows down the roller, thus increasing the current draw, which signals the bot to go into its next state in its FSM
- Our kicker's quadrature encoder is sometimes finicky after kicking (loses counts, or something). The current draw is checked to look for a stall, if it is then abort the kick and return. This has saved us from some penalties for extending past the frame for more then 2 seconds.
Then there is the PID control feature for encoders.
Using the position control mode, in auto the FSM just tells each side how far to go, then the Jags go there (unless preempted by the roller state).
Using the Speed control mode, in tele mode the driver's stick is no longer a % voltage, instead it is a % of full speed. So, what that means is if you get into a pushing match, for example, the driver doesn't have to move the stick any further then it already is. The bot will automagically start to apply more power until the obstacle is cleared.
Could all of this been done without CAN? Sure, but it would have required more electrical hardware (4 current sensors and a better encoder) and more software robot side ( PID controllers for speed, and distance)