I prefer it to user-controlled trading sites, personally. All games - especially older titles - have higher value there than anywhere else, and you don't need to worry about fussy traders overvaluing their titles. If you don't agree with the point prices, you simply don't request them, or don't offer them.
My one complaint is the feedback system, which doesn't hand out proper punishment to traders who send out the correct packages (a user requests a full package, but the seller only sends a disc, for example) or who send out the wrong game. In contrast, a user who receives an unplayable or pirated disc gets their points/credit refunded back from the seller. Fortunately, I've only met one deadbeat who sent me a beat up disc instead of a complete game. Every other trade has been close to flawless.
Goozex guarantees satisfaction in the case of a deadbeat trader. 99% of the time, all it takes to beat a deadbeat buyer or a deadbeat seller is Delivery Confirmation or sending a copy of the game to Goozex for inspection.
Again, it's a great site, and you're guaranteed to get decent value for your games. Points are determined algorithmically, which works fairly well for recent or near-recent titles, but there are still quite a few older titles whose points values are a far cry from their actual market value. (The limited edition of Metal Gear Solid 3: Subsistence is asked for at 400 points - approximately $20 - in contrast to the $200 it often yields on eBay.) And, speaking of older titles, the only "older" platforms that are supported are PlayStation and Dreamcast.
Highly, highly recommended site. Honestly, on sites like GameTZ and the like, I continue to use them, but most of my recent offers have either been people requesting Gamestop prices for their used titles (shipping and Paypal fees not included, of course) or people trying to get full price for a game immediately following a universal price drop.