i like to keep all my saves, even if i'm probably never going to play the game again. the crazy thing is some games (like serious sam hd) use steam cloud but don't sync your saves!
i wouldn't pay for steam cloud to keep doing what it's doing or to support more games because i could just do a little research and write my own program to back up my saves for me. oh wait, i already did! well, mostly — still have that automation thing to do.