For the most part, no!, i would say that the E8400 @ 3.6 or greater is the sweet spot and most setups will not have a bottleneck effect, save for the insane SLI or Xfire setups (295 GTX SLI, and i'm not even sure there would be too much of a bottleneck here either). As Sedaine said, it might differ between games/resolutions, but all in all, you shouldn't see a bottleneck, that is still a great CPU for today's standards.
To put it simply, i have an E8400 OC'd to 3.6 and 2 X 4870's in Xfire, through all my testing and games, i have not noticed a bottleneck where i would say that the Xfire setup should be working better...