I finally got tethering to work on both USB and BT & Internet Sharing. The secret: make sure you run pocket internet explorer on the Mogul before you hit "connect" on the Internet Sharing app. I had the most difficult time before reading a post here about someone starting PIE before running Internet Sharing. I said - why not give it a try and by golly it actually works!

DSLReports speed tests confirm the obvious - USB tethering is faster than BT [588 k/bps] v. [422 k/bps]. I'm sooooo happy!