Well even if you were to buy the box version of F1 2012 it comes with steam support. The only difference between the two is that buying through steam you will have to download the game where as the box version all you do is install it and you don't need to use up your monthly download quota (if you have one). Now Steam itself as a program is great. It provides an easy way to purchase other games at cheap prices and stores them in what you could call a digital library meaning that once you install it you do not require the disc be in your PC at all times. Steam being installed in your PC will only take up a few Mega Bytes, it's not a big program to have installed and does provide an easy way to play all your games.
Basically what I'm trying to get at is Steam is great to have on your PC if you enjoying to play games if you are a "casual" or "hardcore" gamer. Even if you bought the boxed version you still to need Steam. The game comes with the installer already on the disc, The last two F1 games had GFWL (Games for Windows Live) which is basically Xbox Live for PC but worse. Which made patch updates for the last two games few and far between. So this year Codemasters went with Steam support for the game making better,easier and cheaper to buy and update the game. I'm not sure what else I can add but please feel free to ask more questions if I have left something out.