Back in January of 2011 it was announced that TransGaming would be retiring Cedega, the proprietary software formerly known as WineX that began as a fork of the MIT-licensed Wine. Cedega was to be succeeded by GameTree Linux, but this new TransGaming project hasn't been making much headway...
I tried Cedega and WineX a long time ago, but ended up with CrossOver and eventually Wine instead, since Cedega wouldn't work with one of my games. Cedega is meant for end users, and users shouldn't have to install developer tools like GameTree to get access to Cedega. Treating users like developers is one of the main complaints holding back Linux.
I remember many years ago successfully using Cedega to run certain games that wouldn't run at all on Wine due to lack of proper Direct3D support. The last game I ever tried on Cedega was Guild Wars, and after a few builds it worked pretty well. I still wouldn't recommend them to anyone, though: instead of using the same license as current Wine and collaborating with Codeweavers, they went proprietary after forking a very, very old version of Wine.
They're a bad, bad company that thinks they know something about how to run a business, but really, they are clueless. Looks like they're headed into $0 value territory. Good for them.
Now, they do games for the fourth phone providers in france (and tv by phone) with the name of gametree. So don't think they don't have money, they just don't care about linux, they care about money.
(And all their games curiously work fine with wine.)
If you are looking to run some Windows game binaries on Linux, you're best off using Wine and/or CodeWeavers' CrossOver. At least with Valve coming to Linux and other game publishers following, hopefully in the coming years Linux gaming will reach a point where using these Windows binary compatibility layers will become rare.