Simply press f8 at boot to get the menu and then choose last known good configuration or last settings that worked.
The problem with that is it is resets
every time you have a good boot. So, if you have rebooted successfully twice since the failed update, that option will not work. And while I admit, there are other, relatively simple ways to roll back a failed driver update, SR is even simpler.
Also, you cannot undo changes made with the Last Known option, but you can undo changes made with SR.
As far as disk defragmenting, I suppose that's an issue but I never defrag without purging my system of temp files first - and that includes old restore points. Because temp files are stored on the HD every time you use the computer, especially when you access the Internet, and because I think it pointless and even counterproductive to defrag with a bunch of tiny temp files on the HD, I'm not a fan of automatic or real-time defraggers, and don't use them.
And speaking of Windows Update, though I have not (yet - knock on forehead/wood) had one fail with Windows 7, using SR to recover from a botched update is also pretty simple - but not possible if disabled, and may not be possible with "Last known good configuration".
I'm not saying you are wrong to disable it, but if you have because of past experience with XP SR, then I think you should reconsider SR in Win7.