With Vista SP1 RTM'ing (release to manufacture) I decided to install it on my work laptop, the Toshiba R500. The Windows Vista SP1 Update is around 550MB and it was an absolute breeze to set up. It took about an hour and a bit to finish up and after a few restarts I was ready to use my laptop again. After the first few hours of use I did notice a performance increase with applications loading up faster. Resuming from sleep mode also is quicker and the lag when logging in isn't there for me anymore. One of the things I noticed pre-SP1 that I found annoying was viewing images in the photo gallery. Whenever I use to click on an image or photo it would take a while to load up the image but now it loads up straight away. Copying files is definitely faster, I tried copying from an external disk and from the network drive and was happy with the results.
SP1 is great for IT Professionals because it will make your life easier around deployment and management of the technology. You will be able to maintain a single WinPE image because you can install 64-bit versions of Vista from a 32-bit OS. There is improvements in BitLocker drive encryption, it offers a multifactor authentication method which combines a key protected by TPM with a startup key on a USB device and a user generated PIN. There is also improvements in patch deployment and installation times for updates. There are many more changes so check out the plethora of improvements in Service Pack 1.
Microsoft, Windows Vista, Service Pack, SP1, Vista SP1, RTM