I didn't recognize a performance boost in my SP3 Tests.
There is only one security patch in SP3 that hasn't been released as single patch/update yet.
It disables i2omgmt. you can check via start -> run -> "msinfo32" whether it is enabled on your system:
look at SoftwareEnvironment/SystemDrivers/i2omgmt - if it said started "no" you don't need that fix
Also:
You shouldn't have Intel (intelppm.sys) !and! AMD (amdk8.sys) Cpu drivers in your XP installation. That could lead to Bluescreen and endless resetting.
MS Knowledge Base:
http://support.microsoft.com/kb/888372
or easier: vbs script by Jesper Johansson (Ex MS Staff):
http://www.heise.de/ct/08/12/links/044.shtml
in german, second link (the first one is interesting too: allows to fetch all updates from MS for different Win OS and Office at once, making iso files, for doing offline install - pm me if you want help or info about this)
hth
gomi