I agree, Steam is not compatible with capped connections.
I still like boxed copies as well, there's just something great about unwrapping an epic and lovingly crafted game like Dragon Age and then having the box displayed on your games rack.
Uncapped and Steam however makes it very tempting to just buy everything online because its incredibly convenient, and it just gets more convenient the better the quality of your internet. When I got 4mb, I just started buying everything on Steam, the guys overseas have it even better. I don't have the patience to wait through delays or for a courier to arrive. I want to play and I want to play the second the game is available =)