iPhone tethering for me has been iffy, I haven’t been able to get the hack working with the carrier file no matter what I do.  I’m currently running version 3.1.2, but I’ve found a really good solution to iPhone tethering.  I’ve tried PDAnet as well and even bought the registered version but nothing has worked as well as iPhone Modem 3.  Of course you’re going to have to jailbrake your iPhone but it’s well worth it.

The app is available through Cydia but you’re going to need the host application as well.  It’s available for both Mac & Windows and it’s very easy to setup.  All you do is download the host application, run it, and it’ll set everything up for you on the host side.  Then when it says open the app on the iPhone, go ahead and open the app and it should automatically connect and you’re good to go!

When I ran a speed test [SPEEDTEST.NET], I was able to get about 1.9mb down and 700kbs up, which might I say.. is pretty good when you’re tethering your phone.

[iPhone Modem]