I don't remember where I read it, but I remember 4G usb tethering was supposed to be allowed. I guess I read wrong. This was before the EVO was released so I'm guessing that changed quick. I was under that impression too.
I was just loving the fact I could turn on 4G and then hit "usb tethering" on the phone when it popped up and it just worked. PDAnet works, but it tends to cut off alot and sometimes does not want to connect even though your settings are right.