I am new to the iPhone and got a 3GS on release day. I used the BenM hack which worked great. There are many features that I like in 3.1 and iTunes 9 so I upgraded. I only use tethering every few months when vacationing on the northern California coast where there is no Wifi or broadband, only a 14.4 kbps dial up. My solution is to put my iPhone sim card in my old Treo 750 and then use Internet connection sharing. This works but I admit it is a bit of a cumbersome solution.