I have two guys I don't entirely trust. One of them I don't trust if he DMs. Monsters have an inordinate number of 20+ initiatives, near-maximum hide checks, area dispells which happen to not dispel 5 spells and then succeed on the one permanent spell I have that annoys him (arcane sight), beholders auto-succeed move silently checks (something we found out he was doing for them after we asked if we could hear where a beholder had gone - and AFTER we'd already been ambushed at night by one...), orcs (normal grunt ones) beat out feint-in-combat bluffs of 21 etc etc. However when he's playing, I've not noticed any sort of inordinately high-numbers trend.
Why do I keep playing? I like all the players, and it's probably better than the other roleplaying game I actually get to play.
The other one seems to cheat all the time. Lots of very high initiative rolls (as player or DM), an average of one threat a round from the bad-guy side (as DM), rolls that are pre-rolled when I'm not looking (as a player) that sort of thing. When he's a player, I just adjust accordingly. To add to it all, the current adventure he's DMing is whispers of the vampires blade, which I can heartily recommend to anyone who wants to feel railroaded, frustrated and stupefied by the dumbest plot in an official module that I've ever seen.