I saw the slo mo on sports centre. Yeah, it might have hurt a bit. In real time it didn't seem that bad, but you can see why he'd be concussed from the slo mo.
Did you see Laila Ali? I saw the end of her fight as well, I'm pretty sure I've never seen any other boxer completely stop what they were doing because their nose got broken. Basically the ref had no choice then.
I haven't seen any fottage from Holyfield's fight, but all reports seem to say it was pretty boring.