I grabbed a D3 in the Bay Area of California and tried this hack. It worked flawlessly though I wasn't able to test it for more than a few minutes at a time. That phone was defective, though, and I swapped it for a new one. I had to wait until I was back home in Hawaii to try this on it...
No go. It did the 3G on/off thing when a device was connected to it. I double checked the changes, switched from Global to CDMA and back, and generally poked at it but nothing worked.
I got adventurous and did a factory reset. That did the trick. It did NOT overwrite these changes and the hotspot worked for 15 or 20 minutes before the data connection was dropped. I only tried it once as I was out and needed to get home: no cell service here at the house.
But... 15 minutes is enough for me. I only use it for emergency tablet access when on the road - which isn't that often.
Does anyone get flawless, unlimited hotspot action out of this? I'm really curious what the variables are.