@Insead

Really? Really?

N900 can torrent stuff, with a GUI! The horror!!!
N900 can play games and emulators, and with a keyboard and wii support it is actually playable
I am sure you can use IPtables or something to share the 3G connection
Why would you put the N900 in a case? It goes in your pocket....

Oh, and you can't do any of that stuff without jailbreaking your iphone, which no matter how safe it is is a risk.