To add to this, buying the "limited edition" won't get you all of the content: http://www.31012.com/images/games/12/scpreorder.png

Instead, you have to dish out $80 for the "deluxe digital edition" which is of course only available on Origin.

Dammit, well.... EA has the Sims 3 and Sim City 4 on Steam. I think they only did it with massively high selling games like Battlefield because of Steam taking 30%.