If you are like me who moved to Windows Vista early, the two biggest pain areas you would see are Outlook 2007 performance and time taken to do file copy operations. I will never go back to Windows XP but Vista should have done better on these two day to day areas.
What used to take like few seconds to copy from your hard-drive to a USB thumb-drive (or vice versa) in Windows XP, takes several minutes (or even hours as estimated by Windows Explorer) in Vista. Now with Service Pack 1 for Vista RTMed finally, help seems to be on the way for file copy problems. Microsoft is claiming over 50% to 1000% percent improvements in file copy performance. RTM bits are not yet available for download, so stay tuned for a world-wide verdict on this. In the meanwhile if you like to understand the under the hoods technology on how file copy works in Windows XP, Windows Vista and improvements in Vista SP1 read this indepth article from Mark Russinovich