I've seen them run well (outstandingly so for a pbp where nobody knew for ages who was a PC and who wasn't) and I've seen them run badly. However, the most egregious example was a text-book paragon of physical superiority, better than most of the PCs at most things they could do with plot lines hanging off him like armour.
It had all the warning signs of an impending disaster until the only female player, playing the only female character decided 'stuff this' and that since he was the best example of manhood in the entire village, she would marry him.
Suddenly, there were no secrets, he became hen-pecked and was the butt of many a joke from the rest of the PCs. Suddenly, adventuring with him became fun but for none of the reasons the DM wanted.
He left without warning one night and, cursed by his jilted bride, we never saw his like again.
My thirty years of gaming haven't burned me; they've taught me never to underestimate our fellow players' ingenuity at overcoming problems set by our DMs.
