The way PBO works (at least from what I can see on the surface) is it will internally bench a few cores, run them at 4.4ghz for example. But it will have an 'all core' speed ready which is on average 200mhz lower. So it fluctuates a little bit based on what you are doing but there is no noticeable performance 'stutters'. For a one button auto-OC it really decent.

It also turns out the CPU I had was faulty too. Hoorah for quality control gone bad.