I have tested XP SP2 at work on some workstations and it has reduced workstation speed by up to 60% and reduced internet downloading speeds by up to 50%. This update is a surefire way to slow your system down. I recommend you do not update with this patch until MicroSoft has ironed out the known problems with "severe performance reduction".

This said - you can uninstall easily without too much drama. This is one patch to avoid for now.