Despite what I and everyone else has said, apparently Windows 7 SP1 did make at least some fixes that at least some users will notice. I found an actual improvement that was made after I installed SP1. I'm not being scientific here and it's possible something else made the fix, but it's quite a coincidence if so.
I usually keep my laptop (a Dell Latitude D630) docked but open, using the laptop's screen as a second monitor. In the past, when I undocked my laptop while it was turned on, Windows would show maximized windows as the full size of the laptop's screen—including the taskbar. So the bottom of an application, including the down scroll arrow, was hidden under the taskbar where I couldn't click it. The same thing would happen again when I re-docked the computer. I could fix it by resizing the taskbar then putting it back, so it wasn't a big deal, but it was noticeable.
But today when I undocked, I automatically went to resize the taskbar to get things back to their proper sizes, but noticed that I didn't need to. The maximized application fit like it was supposed to. I haven't made any other changes that seem likely to have fixed the problem—I haven't updated the graphics drivers or anything.
Windows 7 Service Pack 1 Beta: World's Shortest Overview of the Simplest Upgrade Ever
Windows 7 SP1 exactly as exciting as we thought
Q. Can I upgrade from the Windows 7 SP1 beta to the Windows 7 SP1 release candidate?