Steamworks isn't a DRM, it is a bigger thing like framework. It contains Steam DRM, but much more importantly it allows achievements, leaderboard, storing saves in the cloud, that kind of stuff.
Steam DRM is actually one of the less intrusive DRM solutions available now. We decided not to add any third-party DRM like Tages, Proactive or one of others to the game (some titles on Steam have a third-party DRM and some don't), so if you're anti-DRM you can be assured we're not trying to limit a freedom of legitimate buyers while trying to minimize piracy.
As it was already mentioned many times, after installing a Steam game and running it you can switch Steam to offline mode and you won't need to connect to Internet to play. Of course achievements and other online features like cloud stuff won't work, but you'll be able to play the game wherever you want, on a laptop in a middle of a forest if you'd like to. Personally I find this cloud saving very convenient, you can play on different PCs and have your progress synchronized. Of course Steam also means automatically delivered updates so don't forget to connect to Internet sometimes to make sure you won't miss them
