I did my very first Gdkp run yesterday, and it was loads of fun! A guy in my guild had collected a decent group for 25man ICC, and we did a couple of heroics too like Marrowgar, Gunship, Rotface and Valithria. The end result was one of the most fun pug runs I've ever had, even with some wipes and other things that usually lowers morale.
So what is Gdkp? I'm sure you've stumbled across it somewhere, it's becoming quite the hype nowadays. The general idea is that it's a regular run, but all the loot is bought instead of rolled or otherwise distributed via some loot-system. So if something drops that you really want you simply bid on it and hope that you're the winning bid. There are several things about it that makes it a really fun and good system.
First of all, the final amount is shared at the end of the run. This prevents anyone from nerdrage quitting or leaving because "mom said so" or other non-valid reasons. And even if someone does leave, it only means everyone else gets more of the money!
Secondly, this is probably among the best ways for someone to gear their under-geared alt. No more having to have 5800 gs to be able to run ICC. Just tell everyone you have 50k g to spend on gear and you're very welcome. The overgeared people don't feel like they're boosting slackers, since they earn money from it in the end.
Thirdly, seeing a good item going into bid and people go into bid-war is quite amusing. And it's an adrenaline rush if you're in it yourself.
Fourthly, no one will roll/claim an item just for the heck of it, unless they're really rich. In normal pug runs you might lose an item to someone that will use it for their "off off-spec" and that's no fun.
Fifthly, you might get nice gear for really cheap prices if you're lucky. Yesterday I bought Zod's Repeating Longbow for 100g! No one else wanted it so I got it cheap, and didn't have to waste a roll on something no one else wanted. If people use penalty rolls one roll is worth way more than 100g imo.
Sixthly, some people have their BiS gear in the "wrong" armor profficiency. But as long as you're the high bidder, no one will complain. Yesterday a shaman managed to get a cloth item (awesomely itemized for ele shammy), which would otherwise would have made people grumpy.
There are different ways to go about doing this kind of run. What we did yesterday meant everyone shared on the totals in the end, even the badly geared people. To be honest we had no one who had really bad gear, I think 5500 gs was among the lowest. I did see in trade today however that some do this by having half the raid as boosters with awesome gear, and half the raid as buyers with lousy gear. Only the boosters get to share the money in the end, on the other hand this gives even less well geared people a chance for some nice loot. We wanted a decent raid since we were aiming to do some heroics. These are all factors that can differ widely in this kind of raid and depends on what kind of buying clientele you want to attract.
Some people argue that buying gear is wrong. The only reason I can see that this is a valid argument is in that since everyone participated in the kill, everyone should have equal opportunity for the gear, not just the rich people. But since everyone who joins this kind of raid knows what's it all about, one can't argue that it's unfair. Hopefully you'll only join if you actually have some money to spend, and feel that it would be worth it. No one is forcing anyone to anything. But some seem to argue that the whole concept of spending money on gear is a bad one, immoral in some way. But people readily spend 5-10k gold on crafteds? This is the exact same thing, only you spend it on bops instead of boes. Even if you are outbid on an item, you still gain from it, since a part of whatever that dude paid for it will end up in your pocket. So even if you lose you win.
We started out yesterday with a start bid of 100 and raising 100. We quickly realized this was too cheap and made it start at 500 raising 200. Some items were sold cheap, because only one person wanted them, other items like Dislodged Foreign Object hc went into bid war and sold for 8,2k. Still cheap actually. Alot of people would easily pay that sum if this item was on AH instead, and way more. The difference is that on AH you'd be fighting against every other caster on the server (and faction). In a Gdkp run you'll "only" be fighting against every other caster in the group.
I noticed yesterday too that people were being cautious about bidding at first. I was one of them. One didn't want to feel stupid or whatnot by bidding a high sum of g on some gear piece. What would everyone else think? "haha he's paying 4k for that ring, what a schmuck". But if it's an upgrade it's an upgrade, and only you can decide whether it's worth it or not. 4k g for someone who has 200k g isn't much. 4k g for someone who has 5k g is quite alot.
Sure one can argue that whoever has the most money gets all the gear. But the feeling I got from yesterday was that whoever wants the items the most, gets it. And honestly that is exactly as it should be. In the end I think this is the best way to distribute loot within a pug that I have tried so far, and I highly recommend you to try it out! Just make damn sure you trust the Raid Leader ^^
EDIT 20/8: Could be worth knowing that we each earned 2300g from this run (minus whatever one had bid on items of course). And that was from cautious bidding, so it should be seen as a minimum.