Kinda neat, but I'm not sure about the config file thing. If I log into Steam on my Macbook I want to play in 1280x800 and if I log in on my PC I'll want 1360x768
If the system is smart enough (and coming from these guys I expect it is) it will keep track of certain variables and change the settings depending on your system. Even now you can encounter not just resolution issues across machines, but performance issues as well (graphic detail, EAX, DX9 vs DX10 options).
Actually, scratch that: Given DX9 and DX10 differences, the system must take into account not only configuration but also such instances of incompatibility.