I believe the drivers on the CD and the ones available for download are for 10.3.6. If you have 10.3.7 the installer won't install new drivers, but it will install the ATI ROM Xtender file, which you'll want installed as it controls the card's fan. One thing you can do while you wait for the card is to download the January 2005 drivers and run that installer. It will install the latest ATI ROM Xtender. Then when you get your X800 XT you can just plug it in and have at it.
The CD does come with a new version of the ATI Displays application, which is an optional install component that allows you to take advantage of some of the features mentioned in the various reviews like TV Out, Versavision, and 3D Overrides. So if you want to take full advantage of the card, you'll still need to install the ATI Displays, but it isn't required for standard functionality.