I've had Steam for almost 2 years now, and have bought and played Left 4 Dead 1 & 2, and COD MW2 through it. I didn't like it at first, but after living with it I must say I have grown to like it. Steam is simply a digital delivery service, it puts the game on your computer just the same as a disc would. You have the option to launch the game from Steam similar to GameSpy and X-Fire. And like those 2 other tools from there it is done. EVERYTHING from that point forward is the game and your computer's ability to run it.
When I clicked on start in DX10/DX11 it installed a newer version of DX9 (I had made sure DX11 was up to date prior to install but not DX9) because the game developers dictated that a certain version of Direct-X was required to play this game.
I can certainly understand that needing Steam is initially frustrating to people who aren't interested in multiplayer. But once you're used to it, and discover it's not the root of all evil, you'll at least be ok with it. As Senethro said above, change the settings to turn off the advertisements, and updates if you wish.