Never had any problems with IBT. Infact, for me it has been the defacto stability test for quite a while now.

My current setup 2500k@4.7GHz has been proven stable initially upon building, and the later on when upgrading to a new bios. Running 1.32v with Silver Arrow, and my temps hover around 70c. EIST is also enabled so it's not 4.7GHz 24/7. I'm accustomed of leaving IBT running while I sleep. So my standard run is around 6-8h.

My overclocking has always been about finding the sweet spot for daily use, and not the very far end for cpuz validation screens. I gues that means I'm not that xtreme. And from the looks of it, 2500k will remain the last pinnacle of overclockable cpu's. There will probably never be such chips in the future, which makes me sad...