ran stonecore as my first dungeon in cata with my warlock. the tank was nice enough to explain all the fights and everyone listened except for one hunter who didnt follow kill order and a rogue who was extremly stupid, stuck in WOTLK. he would always break CC and when i told him i needed to cc and he needed to cc he would just say "just aoe it all down quick". worst part was during 3rd boss he killed himself by attacking melee when he wasnt supposed to and blamed it on the tank.
i did really enjoy the boss fights but i can tell im going to have to find a guild...
Grouping with bad PUGs is good practice for coping with situations in which good players make mistakes, because that will happen, even in guild groups.
It also makes you recognize and appreciate when people play their class well, and hopefully it rubs off.