My DM's have been pretty good, except we had one really boneheaded DM moment:
It's a great campaign; loads of fun, old friends, clever plots, neat dungeons. We all start with 4 levels of NPC classes before our main classes, which makes it a little low powered, but all in all, game is pretty good. I'm playing a crafter Adept 4/Wizard 1/Mindbender 1/X1/Mystic Theurge 1 (Can't remember what the X1 was, but some other free lunch prestige class). I'm reasonably potent, partially because magic items are worth X4, so I can sell them for lots, barter with my party members, and pretty much have quite a bit past WBL gear.
So we're off exploring some ruined temple on a lost continet which we boated to, and we find this orcale. We end up freeing the orcale, which requires me to take it's place. "No big deal, I'll just creatively magic my way out." I end up almost trapped, except the party can kill me and then use an orcale-granted-wish to revive me.
As a practical joke, they revive me as something random. My DM rolls reincarnate, gets "choose one", chooses Yak-folk for his own amusement. I'm like "well, that sucks; I unqualify for one of my prestige class" and the DM goes "Well, since this is forced change, I'll let you keep your feat and skills from being human."
Bam. I am now a 5th level adept/4th level wizard casting with +7 Natural armor, large size, strength of 26, con of 18. I immediately became approximately powerful enough to take on the party, which caused balance issues as the party shifted good, while my characters alignment was "Manipulative and subtle Neutral and unfathomably evil" Ended up the villain. Was incredibly fun...but there were several moments where it was clearly DM mistake.
Same DM tried to do Morrowind style "After first adventure, you get stats based on what you did." But tried to adhoc it. Most charismatic/boisterous/active players got +8-+13 to their base stats over all, (13's and 10's), quieter players got +1's - +3's. We quickly were like "Uh, let's do a redo on that one." and divvied up ~7 pts to each of us (at a 1 to 1 ratio).
Still, aside from minor mistakes, my group has been wonderfully fun and wonderfully great...which makes me all the more amused at reading these stories.