I use system restore on my Win 7s to back up some of the critical bits in the OS.
I use external hard drives to back up stuff I entirely control like data
System restore has bailed me out when things no longer work for some mysterious reason (one of many things got loaded on my computer and it didn't act up for days).
My biggest problem is trial and error what program change is causing the newly developed problem. It seems I only have one restore point available to choose, that being the last one (typically a MS auto).
I tried making additional restore points as I go along, but anything more than one gives me the error insufficient memory in spite of the fact that I have oodles of free space on my OS drive.
My recourse is to spend the time to clone the whole drive a couple of times a year so at least I will have an old restore to choose from.
Being a simple minded user, I'm more afraid of screwing things up even worse if I try to trouble shoot stuff deep inside. I prefer the simply click on "restore" to set me right even if I give up a new program or two.