Steam's DRM is the least intrusive/pesky/annoying I've dealt with, and in the case of many games, non-existent. I'm a big fan of Steam for various reasons unrelated to DRM, but it's certainly never done anything "nasty" to any of my computers it's on (it's on all of them). Only time it can become annoying when gaming is if it's on a computer you travel internationally with frequently, or if your internet connection is intermittent (though there's workarounds for that one). Many games have DRM above and beyond Steam's, but they'll have that DRM no matter what form you buy them in.