Yes, Steam is DRM in that it's required to launch the games, many games bought through Steam can still be launched without Steam running though, but it's not annoying, over complicated, buggy, broken, limiting or intrusive like say, SecuROM and StarForce have been known to be, I bought F.E.A.R day one, took me weeks to get it working because SecuROM either wouldn't recognise my DVD drive or would bug out and crash the game on start up while reading the DVD.
I'll most likely buy it off Steam is it does end up being customisable, so I won't have to send out a search party for my CDs after each format.