This snapshot also nerfs xp factories a little. They can be used but if used too much, they will stop working for a while. To quote Dinnerbone:
The new mobspwner xp mechanic resets every so often. You can still grind exp every now and again, just not for 1000 levels in 2 hours.
The goal isn't to stop you from using them entirely or punish you even, it's just to dissuade you from using them all the time vs other ways
As I said, this isn't to stop them entirely, just not usable more than once every few minutes.
It doesn't affect item drops at all, don't worry about those ;D