theres quite a bit of info about sp3 here
http://www.winsupersite.com/faq/xp_sp3.asp
http://www.winsupersite.com/faq/xp_sp3.asp

This pre-release software is provided for testing purposes only. Microsoft does not recommend installing this software on primary or mission critical systems.
Reminds me of Live at the apollo the other night with Dara O'Brien.I don't think it is designed to 'fix' your systemif it aint broke don't fix it and mine aint broke.
Most updates are security or driver based.