Um it is actualy useful if you don't want to reformat. But For me, I Have it turned off.
There is also ASR, Automated System recovery, you need to create a full back up image for that to work.
If it was on then yes there should be check point for the first day, Documents and files will be left alone, only things that are affected are like service packs, Drivers and programs, I think, I could be wrong.
According to Comptia the Tools used to trouble shoot/fix a computer from First to Last.
Cmd>DR watson>Safe Mode> Recovery Console>System Restore> ASR> Reformat/Reimage.
"IF" I remember correctly.