The AT&T Sales Representative was the one that told me about:
http://help.benm.at/help.php you have to do it from the iPhone or else you will be linked to a different site. Just follow the simple steps and download a simple patch for AT&T US. After that it will work without any problems.
I've used it on my iPhone 3GS since the day it was released, upgraded to OS 3.0.1 and it continued to work. I am a little worried about release OS 3.1 as I've heard the Beta 2 version crippled Tethering Completely. Will have to wait a couple days before trying again.
DSL Reports for my phone are showing speeds in the 900kbps to 1.2mbps range. Being in Emergency Services it is really awesome to not need a CDMA type card for my computer, all I use is my USB Sync Cable and the iPhone Tethering happens auto-magically now.
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