It makes sense that to play a game you bought on steam you have to have steam running and be on the same account you bought the game with. I don't see that as DRM any more than having to log into this forum with your account to post.
Also from what I can tell you get your activations back if you uninstall the game. 5 simultaneous installations. Since when will you have the game installed on five separate PCs at once? :P
I don't have too much of a problem w/ the 5 install limit + revokes allowed (b/c revokes are allowed) - many other games do it, i.e. many of EA's titles. And I have bought many EA titles, over the years.
It's just here w/ DKS Steam, that could be possibly two DRM's running, as opposed to one. Steam DRM is enough DRM itself. Steam DRM + Securom DRM is just pretty much redundant.
Only benefits of Steam version is auto-updating, back-up archiving, friends list, screen-shot taking, and the 3 extra exclusive armors. Most of these Steam-features (except auto-update and archiving), you could do so by adding it to Steam as a Non-Steam game, if you buy it elsewhere.
It's still something I'm debating - do I buy it from Steam? Do I buy it from Amazon (and avoid Steam)? Do I buy it from D2D? Or do I sit and wait for more price-drops?