Here it wouldn't be a problem since I run XP on one drive and Vista on another without a dual boot configuration where XP could be reinstalled separately. For those depending on XP with a number of things like downloaded programs the wait for the final release would be the best move for them since this contains all of the more recent updates they would have downloaded anyways with the auto update option enabled.
If you just reinstalled XP by chance you can download and save this release to a folder on the drive for installing afterwards unlike what was seen with SP2 when that came out on the update site. There you had to run the installer right away or find a page like the one there or at softpedia.com for downloading the redistributable package.
http://www.softpedia.com/get/System/...-SP2-RTM.shtml
It's still a good catch since SP3 has been long in waiting for many. Although MS may most likely add a few more things by the time the finished release is available you can grab this for now and store in a safe place if you need to reinstall Windows while waiting instead of going after some 93 seen as of late.