He can sit at quake 3 for an hour fine, but the effects in osx make him feel sick (so he turns them off).
Edit: I just emailed him and iOS 7 is doing his nut in as well. He's switched back to his 4S with iOS 6 on it.
Interestingly enough, iOS didn't have any "distracting" animation (for me) until iOS 7. Nothing that I'd wish to turn off. It was just "slick" and "natural." It also had that "stability" of the interface -- once you see something then nothing disappears or moves "just so" or "creepily on its own" only as the result of your actions, so nothing had the "creepy unnatural slides or transitions" whereas Windows was full of exactly such ones since at least XP. I always believed it was only "MS just doesn't have taste." I think Jobs somehow had that deeper feeling how the things should behave (that can be traced back I think even to the influences from his work on video games with Wozniak as he was young -- knowing that the movement can be synced "properly" even with the slow processors and CRT screens, if you really care about it) and now the people who do implement the transitions don't do it to that "ultimate naturalness" goal.