I've been lucky so far, it would seem.
The worst I've seen is someone who dropped out of the tournament after my Rexler managed to wipe out his named-tie list (minus Omega) after both my Omega and Zeta were killed. He looked pissed, but that was his 2nd loss, and I guess he really wanted a shot at the cut. At the same tournament, another opponent dropped a "I'd wish you good luck, but I wouldn't mean it."
Since I'm going to these tournaments with my 6 year old to teach him that perseverance, respect, and class are important, I'm just not going to that store anymore. Thankfully, he was playing his own game on the spare table for those two instances, the first one 'cause he's a horrible winner (we're working on it) and when you feel like you really messed up, having a kid point it out doesn't help.
We're lucky to have many LGS around here, and quite a few of those are FLGS!