So long as the FPS is locked, I don't care what it is. In fact, I'd be fine down to 20. The real problem is when they dip, as I can easily notice that.
On some games I don't mind the dips. Like in SSF2T:HDRemix, the dips make me think that I just pulled off some massively cool move and hit the opponent so hard that his world slowed to a crawl