Possibly worth mentioning to balance out the Apple bashing (for the record I am not even close to being a fan of Apple...) Tethering is something pretty much all smartphones can do, my old WinMo 6.1 could do it, and i'm pretty sure that the iphone has been able to do it from the 3G onwards.
It's purely a carrier decision as to whether they allow you to do it or not, and even then they aren't consistent.
For example, Almost at the same time I and my old house mate got new contracts on Orange, both similar cept he got a HTC Desire and I got a Samsung Galaxy S.
My Galaxy S tethered out of the box, his Desire did not. After spending 45 minutes on the phone to Orange tech support, they eventually worked out that their policy was to block tethering on the Desire by default until the customer phoned up, but not the Galaxy S.
Go figure...