System Restore saved me many times.
But then I contracted a virus that obliterated the "system32" folder...the temporal lobe of Windows.
...It's also where the restore points for SR are kept!
All data was eventually recovered by putting the hdd in an enclosure and retrieving it all, but my 22 GBs of program files were useless, and I had to start from scratch.
Since then, I have gotten a 120 GB drive, and I've partitioned it into C: -OS & Programs, D: -All my documents, web site development crap, photos, etc, and E: -Backup.
I've also installed Norton Ghost & GoBack. GoBack is located on C:, but the dedicated restore points folder for it (7.6 GB Gobackio.bin) is located on E:.
Norton GoBack is better than System Restore for two reasons; It saves your entire global configuration instead of only user system files, and it presents you with a list of files that have been created or changed between restore points which you can reinstall, like for example the email dbx files.
I use Ghost to clone my C: partition, and now I'm presently exploring the very underappreciated XP backup utility.
System Restore will be disabled for me ONLY because I have GoBack.
If you don't want to spend the time configuring a new backup utility, or if being creative and strategic about setting up a backup "plan" is not appealing to you, then I highly recommend that you leave it running.
But if you either have another backup-recovery program or you're disciplined enough to manually backup your system regularly, then SR is another "write to disk" program that probably does slow your system after changes or during shutdown while it's recording.
If you decide to use System Restore, at least take the time to configure it so that it doesn't impede performance.
A helpful little freeware that is a perfect accessory to System Restore is called "System Snapshot". (Got it from Majorgeeks.com, I believe)
It puts an icon on your taskbar that you can click any time to instantly add another restore point to your System Restore folder.