Not sure about using a restore point in "anger" but I've done so in "desperation."
I've installed device drivers that completely failed and broke stuff, and uninstalling them didn't seem to help. So I used System Restore to restore my computer to the state before I installed the drivers. It worked. All three times on two different Windows 7 computers.
Keep in mind that if your system restore doesn't work, you can always undo the undo, so to speak. Or roll back to an earlier time. It is a pretty flexible system.
Just make sure to create a restore point before installing stuff. A lot of installers do force a restore point to be created during the installation process, but some don't.
Regarding the safety of your documents, my understanding is that System Restore uses the Volume Shadow copy Service to back up system files only, so your documents shouldn't be affected. I've had no problems.