The Live is working well for me here in California on T-Mobile. Here's a flight from yesterday:
http://www.flytrex.com/mission/quadcopt ... ver-48782/
I had the Core 1 previously and the actual data collected by the Live seems to be just as good or better, but it's nice to not have to hassle with a SD card and uploading and it is very nice to have the "Last Seen" feature. I haven't had a flyaway, but this gives my more confidence for sure.
When I'm flying, this page shows a live, public (my choice) view, including battery voltage:
http://www.flytrex.com/nathan.hoover/live/
I tested it using a second phone and it works great.
$10/mo seems like a fair price. On T-Mobile if you ever did use up the whole 1GB in a month, they scale back to 2G speed which is all the Live uses anyway, so the plan is really unlimited. The only pain with T-Mobile is that since you can't receive texts on the Live, you have to do stuff like activation and creating your account etc over the phone rather than online. I have another SIM card that works out to under $7/mo and everything works online but don't have the Live working on that one yet.
I did one firmware update and it was quick and easy, over the air, and controlled by a page on my flytrex account.
Installation does require soldering the power and ground wires, but beyond that it's simple. I have it mounted externally so I can see the LED. The green flashing is bright enough that you can see it while flying overhead and you know it's transmitting. Here's a photo.