I had a few moments in XCOM the last couple days where I saved/had a save file prior to some catastrophe or losing a soldier, but I didn't reload. It somehow seemed lame, and since I had to buckle down and get through the mission with the remaining guys it made the game more fun. So de facto Ironman, I guess.
I've never tried playing a SS game solo, but it's probably dull. The thrill of playing with other people, though, probably comes from the utter insanity going on around you. That part is worth it.