I've been very pleased with the responsiveness of BFQ when multitasking.
And actually, I shouldn't say I never get lock-ups. There's been a couple times where the DE just freezes, and I'll have to hit Ctrl+Alt+F2 to switch to another tty and restart the display manager. But I attribute that to running bleeding-edge version of things and enabling experimental features, so that's fair.
Lastly, my MacBook Pro (2010 6,2) would also experience random freezes on Ubuntu (would have to power off/on) and upgrading the kernel from the Ubuntu default to latest mainline solved that problem completely.