I'll be the first to admit that I'm something of an instance snob. I refuse to run Brewfest with anything other than guild mates (primarially because I don't need anything, or want anything, from there - there's not even badges for crying out loud), I hate ToC, and the Occulus can get bent. Of course this is on my Paladin - on my alts I'll take whatever I can get.
It's also true that for every bad PuG there seems to be a good PuG - or at least one good PuG member. This is the guy who helps summon, isn't an idiot, or at least does some decent baseline DPS. I personally love seeing a PUG with a ton of Heirloom items as well - because at least you know they put in some time with one other toon - so they should know the basics at least.
My real rant
I hate PuGs that base entrance or acceptance on arbitrary numbers. LF 3k DPS, 2k SP, 30k HP, etc. Of course my true favorites are those that want you to link Starcaller before you can get into a Naxx 10. 90% of the time all this leads to is a busted run. Sure - nobody wants to carry the 400 DPS fury warrior (really - how is that possible?) through a run or a raid - but you won't get that information until you see him play. Hell - I could state that my mage is a 3k mage, and she might be - if I blew all my CDs on a massive trash AoE.
What you dont know is if I can manage my mana properly. Will I be on fumes at the end of a 30 second fight? Do I know when I should use defensive CDs while tanking? Take your chances with the rest of us. Sometimes you get gold - othertimes you get a gold plated turd.
Just because we're successful
Doesn't mean I want to pick out curtains with you. Sure, you can friend me - but don't think I'm going to tank/heal any old heroic for you just because I'm on. Now, if more badge/token pieces were BoE - different story. I've got to earn those badges the hard way on my alts though, and the invites just don't fly in as fast on the old mage.
Finally - if you're in a melee DPS role, and we have to hunt around looking for a healer - then yes - I'm going to roll on that healing neck that may not be 100% itemized for my DPS. Your offspec can go pound sand.