This just happened to me; lost three or four levels and over three hours of gameplay and went back to a save only three hours in; despite liberal use of quicksave.
More detailed: After my SECOND crash to desktop, when I reloaded the game, the only saves available were a quicksave and an autosave several hours old. I believe they were from shortly before my first crash to desktop, but not immediately before (probably unrelated).
I'm not repeating the last three hours of game if this sort of thing is common. Buying it on Steam day one was stupid; like all Bethesda games, they're great, well-written, expansive, etc. but good luck actually trying to play them through the massive amounts of bugs. Better to wait a few months for the fixes to start rolling in.