The best part of steam is for me, that there is no "copy right protection" that screws up my PC or tells me to uninstall 80% of my software! All you need is a connection to the net. Even if you buy the box, the cd is not needed after installation, no switching disks.
I personally love that about Steam.
Join up to the VGC Mario Kart Wii GP European League!
Or the VGC Mario Kart Wii GP Australian League!
Or the VGC Mario Kart Wii GP American League!
Or the VGC Halo 3 American League!
Or the VGC Call Of Duty PS3 League!