EatMyShorts! and CL300 are right: the water system is a weak spot. But there is a cheap way to prevent damage to it and if needed, I can share a procedure with you which is quite commonly applied in countries with rather harsh winters...
The brakes are excellent. Don't know the brakes of the Challenger, but they are really good.
Short field performance has always been a strong suit of the F2000 series and with the arrival of the inboard slats with the S and LXS model, it's even more phenomenal.
I've never had any problem with the APU.
For maintenance, I do agree with what EatMyShorts! wrote. It is my impression that you get a more customer friendly treatment when you avoid the big service centers. For recommendations I prefer sending you a PM.
Don't buy the class II EFB standard issue - they are useless. Forward lav is the thing to have on longer flights and the foldable jump seat (= folds into into the cockpit floor) frees some valuable real estate in the galley. EASy II + adresses some irritations of the previous version.
They are reliable birds with very few problems and great operational flexibility.
Good luck and enjoy!