There's only very minimal speed differences and it turns out it's nothing related to your hardware, so I'd be surprised if people can get the speeds they were getting (without injecting into the client aka cheating which would be very easily seen by Sam) before in previous Mir servers.
Also it's hard to explain but basically, Chronicles was coded weirdly in the sense that if you run past someone and tap shift to melee and continue running, even if you skipped a frame then, as long as the other person taps shift at the right time on THEIR screen, you'll both be hit.
So... yes, pvp is more fair. But with everyone on relatively the same speed, I think wizzies will gain the most out of it :P