Despite it being 12 months since Microsoft released Windows Vista and availability for XP ending in June this year (2008) it's somewhat surprising that a service pack should appear for Windows XP. I guess Microsoft realizes that there's going to be a very significant number of computers running XP for some time and there's just time to squeeze in one more service pack.
The service pack includes
All the updates so far
Improved installer and management frameworks
Improved networking components for greater performance and security
There's little (nothing?) here to tempt you with new flashy bells and whistles, this is all an 'under the hood' tune-up. However there are features to allow XP to work better with the new Windows Server 2008 (NAP) and I've seen performance improve dramatically on some systems after the upgrade to Service Pack 3. So an upgrade is certainly well worth the relatively short time it takes.
