Hard locks occurs very randomly and I've yet to experience it in such a manner when using CFS, but I am able to lock up the device on CFS, in any fashion.

With BFS, sometimes it'll lock up when it's under medium load, other times under no load whatsoever. I'll open the status menu, it'll completely halt. Playing a game, reject an incoming call and it'll be hosed. Both the power key and the light sensor (controlling keyboard LED) are unresponsive and I have to battery pull.