So using back up I won't have to download ANY thing from the steam servers?
How small is a backup for say- something the size of TF2?
Right click the game, click properties. Look under "Local Files", and it'll tell you.
Personally I don't like their backup function, I just redownload what games I'm most likely to play from the start or to keep me busy for the time being and then I download everything overnight.
But I have a really great internet connection, so it's obviously not the same for everyone.
You can copy and paste the Steam directory but there are some games that might just be wacky when it comes to that. Some might need reinstallation.