Windows Gaming At Half The Speed
Everyone needs more than 640K, but there is a point where more frames per second is not noticeably better. For a low polygon count game like Quake III Arena, WineX gets pretty close to that magic number of 60 frames per second. For a modern DirectX 8 game like Max Payne, it does not do quite so well. Keep in mind that these tests were run on mainstream hardware (Athlon XP 1800, GeForce 3 Ti200), so a better CPU or graphics card may help. In general, Windows performance is at least twice what WineX can deliver.
The great thing about WineX is that it is still fairly new, and just like Linux, it keeps getting better. Support for DirectX 8 will continue to improve and the kernel module should give a noticeable performance boost when it arrives. Since you can try WineX for as little $15 (the cost of a 3-month subscription), I recommend it to anyone that is already running Linux. Go ahead and download the precompiled binaries and give it a test drive.
However, I would not expect to play games that do not have at least a "4" or "5" rating. The current list of games with a "4" or "5" rating includes: Diablo 2, Max Payne, The Sims, Jedi Knight 2, Sacrifice, WarCraft II, Baulder's Gate 2, and DeusEx. Civ3 will be added shortly. But don't get rid of your dual-boot just yet. Depending on your hardware, some games may not have acceptable performance, and whatever you do, don't forget to vote.