After dragging my feet for months on this I finally took the plunge and used these instructions to flask my phone during my lunch break. A bit nerve racking as you watch the phone reboot a few times, but if you just let it go everything works out.
I did lose authentication and had to call, but they took care of it remotely. Based on some of what they said I am curious if your location when you flash has anything to do with it. They asked several times where I was now vs where I first activated the phone.
No matter, it worked great and I got my official threaded SMS. Have not tried GPS yet, but everything seems good.
Thanks for posting these instructions