I like steam and I don't. I have tried D2D but hated it. Not only do you have to initialize your game with a CD Key but you have to authenticate it through D2D! If you install the game more then 5 times, you have to contact D2D to reset your account. If you're into modding PC's you know how frustrating it can be when you have to reinstall. Then if this happens on a weekend you're screwed. At least with D2D you download the whole thing and you can save it. Although it's usually too damn big to save onto a DVD and they don't have it split up nicely so you have to do it manually.
Steam is nice since there are no CD keys to remember. You can install it as many times as you like as long as that computer has your Steam info. The downside is, you do not get to save the download file as Steam hides it someplace. Also, I kind of like having a hard copy in case I decide to play it several years down the road when maybe Steam and D2D aren't around. Although I don't think Steam is going anywhere. Not every computer I have is on broadband though.
I think they should have an option to buy a hard copy for maybe $10-20. Otherwise, the only other option is to download a bit torrent and use your Legal key. Then if your ISP is spying on you, they will send a TOS violation and tell you to delete it not knowing you actually paid for it.