May I suggest that if you are thinking of installing it, to wait a few days before installing it, and wait to see if there are any glaring issues with a specific setup (hardware or software) before installing.Service Pack 1 for Windows 7 and Server 2008 is ready.
According to the release announcement, SP1 will be provided to volume licensees, MSDN and TechNet subscribers on the 16 February, then from the 22 February all other customers will receive the update via the Windows Update service. It will also be available from the Windows Download Center.
Also if you have multple computers with Win7, if you have a good broadband connection, get the full download from the Windows Download Centre. Save to a USB stick and all computers can be updated with only one download.
Also, before install do run a quick antivirus check as Service Packs will halt if they smell malware, once you are ok and malware free disable your internet connection (switch off the router or unplug the ethernet cable to the router), and disable your AV and security apps before installing, as this just cuts one thing out of the mix that could block a sucessful install.
so if you have kept up to date with Microsoft updates since you got Win7 there should be very little to update with SP1.This service pack is a relatively minor upgrade. It combines all the previously released stability and security updates, but there are no new features for Windows 7 apart from the support for the Advanced Vector Extensions instruction set.
dave