I wonder if this puts it 'ahead' of Zurb Foundation?
I have this sneaking suspicion that even if Zurb does a 'good' job, unless it's way better, they're never going to get the publicity these guys do, and thus won't have quite the same feedback loop.
Good question, I don't know the answer. Honestly, I've looked at Zurb Foundation a couple times, didn't see anything that looked like an order of magnitude of 'betterness' over Bootstrap, and decided to keep using Bootstrap because of that feedback loop.