Yes, without any doubt, you should install service pack 1. There are no cons, only pros. Of course, like any major update or service pack, back up any critical data before proceding. But you should not have any problems and you will notice a slight increase of overall speed once it's installed, especially with file transfers. Takes about 45min to an hour to install with a couple of reboots along the way. If you are running an anti-virus program, I would recommend you disable the real time protection before installing as some of them will interfere in any system file modifications.
If you are also running Office 2007, I would check for any updates for that as well while you're at it.
Techman