I think the "Make Me An Offer" game is a pain in the ass, but it seems to be the norm around here. Some people genuinely like to bargain hunt and haggle, but for me, it's just a frustrating process. Many people just aren't interested in fair offers. They want to walk away from a trade feeling like they had more than they did going in.
It also seems to be slowing acceptance of the marketplace, which is a shame because the marketplace is infinitely easier to navigate than the trading forum. The trading forum is just so damn noisy with searches because people leave items that are no longer available in their posts, and there's no way to distinguish between "Wants" and "Haves". I've sent out a number of offers to people with stated prices in their lists and didn't get a single response back from anybody. Not even a "Sorry, no longer interested" or "Sorry, that's no longer available."
I don't mind waiting for my game, and I like the idea of spinning the roulette wheel and seeing what gets matched, so Goozex appeals to me. The Goozex Guarantee makes it one of the few sites that actually protects your investment. If somebody scams you on CAG, in contrast, all they can do is warn other traders and ban the user, which gives them absolutely no incentive to come back and resolve what they've done wrong.
I've completed five trades on CAG. One was trading a game on one platform for a game on another. One was a lowball sale. Two were going in on Steam multipacks. And then I got scammed by a user attempting another cross-platform trade because I have virtually no feedback. Any trades more complicated than this never seem to go anywhere. Even before prices or offers are discussed, people simply don't answer their PMs, decide that they're not ready to get rid of the game yet, or don't feel like dealing with a "new" user.
GameTZ isn't perfect either, but the sellers there generally have more realistic expectations since the site is more "user-to-user" oriented versus CAG's "consumer-vs.-retailer" mindset. They also separate the "Make Me An Offer" gamers from the threads with stated prices - "Classifieds." GameTZ has issues of their own, though. There's no enforcement of any kind of Terms of Service, so everybody expects gifted Paypal, game shares and rentals are common, and it's rare to see a portable console available that isn't bundled with custom firmware or a flash card. That might be your thing, but it isn't mine. The site's technically free, but there is a subscriber option, and users there have taken to crucifying non-subscribers at the slightest provocation.
Considering all that, I trade most heavily on Goozex for the following reasons:
1. No haggling.
2. Trades are protected.
3. Requesting/Offering is clean and easy.
I generally don't request new games, have other ways of dealing with poor condition, and don't keep a surplus of points on hand, so the complaints that most users make towards the site are irrelevant. I'm also exceedingly patient in most cases. I'm tolerant of waiting until it's my turn in the queue to get a game. I'm less tolerant when trying to get a response from active members that seem to be ignoring marketplace requests for no good reason.