It has been little over a year since the release of Vista and now the first set of improvements are hitting the streets. Service Pack 1 is now available to MSDN subscribers. As I understand it, Service Pack 1 is mainly focused on addressing specific reliability issues, performance and supporting additional hardware and not being used for new features.  

Here are some things to know about SP1 from Microsoft TechNet:

• If you have a prior version of the SP1 beta installed, you must uninstall it prior to installing the final version. Use the Control Panel applet "Programs and Features" and select "View installed updates" from the top left of the task pane. Under Windows, look for "Service Pack for Windows (KB936330).
• Some TechNet Plus subscribers may encounter an issue with a small set of hardware devices that may not function properly after updating a Windows Vista PC to SP1.   This is an issue with the way the device drivers were re-installed during the SP1 update process, not with the drivers themselves—these drivers worked on Windows Vista RTM and they work on Windows Vista SP1.  This problem is typically corrected by simply uninstalling and reinstalling the driver.
• We are working with the manufacturers of these devices to get the drivers and their install programs updated, and also on other solutions we can use to ensure a smooth customer experience when updating to SP1 over Windows Update. For new PCs provisioned with Windows Vista SP1, this is not an issue.