I for one will not install XP SP1...at least for the time being anyway. There are a few new bugs introduced in SP1 and there is some nasty spyware integrated in this service pack (for more details do a search for SP1 especially look for forum member pokopiko's postings on the subject). Both he an I are BIG advocates of not installing it for the time being...mabey later, but certainly not now.
Besides, most of the bug fixes and updates in SP1 are available at Windows Update. So you don't have to install SP1 to get them.
Do a search of this Forum, read the posts...but in the end it's you who must decide.