Definately depends on damage done/state i was in before, but normally takes about a day or so to get my head back if i've been lucky. During that time I can do simple stuff at a *very* slowed rate (i normally just stay at work) but memory will be shot...
More and more i'm disliking the physical after-effects, the slight muscle spasms feel very weird and of course the raked inside cheeks are sooo painfull
I have noticed though, that unless i've done something *really* major, i never seem to feel much pain on the same day- i've been walking around with broken ribs, and huge open cuts etc..
It's allways the next day or two when the pain hits me...