I buy a game, an episode, my computer's HDD crashes (totally unrelated ), I reinstall Windows, reinstall Steam, and it has all the things I've purchased, right there, waiting to be downloaded and installed.
This pretty much one of the huge pluses for me, although I'm actually really good looking after CDs, I have a command and conquer curse and am always scared it will cross over to other games. With Steam I'm relatively safe.
Seriously, I've lost the original C&C NOD CD, I rebought that. Red Alert 1 case is shot to buggery. I lost Red Alert 2 completely and rebought that. Red Alert 2 Yuris Revenge just refuses to install from the CD.
I've always been fine with all other games, honestly. C&C is one of my favourite games too, it's not fair.
I think if I bought the First Decade DVD it would just melt as soon as I touch it.
The only problem with the Steam thing is that Steam will not be around forever. I mean I still play games that are 15+ years old, they run okay thanks to emulation. Will there still be a Valve in the same period of time? Still be a Steam?
Then again... Do I think HL2 will be that much of a lasting title for me? Not really.