For me its still a 3 or 4 bet push pf, but I have not seen anything but aces on the calls for some time. On the other hand, I have seen KK to AA happen at slightly less frequency than quads.

Last night, two KK push calls facing Aces both times, but at least the one I lost was a half stack (fnord adjusment) and on the other I spiked the K for a full stack :P