So...how does this get my phone off the charger, exactly?
While the product looks very enticing on the product website, ideal perhaps for long plane trips or other times when you have no access to a charging source for a long period of time, I don't see how this product benefits the everyday user. In my everyday routine, I am near a charging source - wall outlet, computer, or car, in roughly 80-90% of my activities. So, then, why would I want this product over the extended battery?
Perhaps, Chrisy can chime in, since she has been a big fan of the extended battery via her posts in the forums. Do you think it's worth buying? Would you buy or use it instead of your extended battery? I guess one would have to determine if carrying around a second device is better than having a phone that has a battery sticking out of it with no case avaialbe for it. Granted, Seidio is developing a few cases for the extended battery, but in the meantime you have to get creative and slide up your gel case if you want a case on your phone.
From my reading up on the product website, it appears that this product needs to stay connected to your phone. It's not a charger, where you charge you phone for a hour or so, then you have 20+ hours of battery life. This thing needs to stay connected to your phone to get that 20+ hours, so how is it different than connedting your phone to the wall, car, or computer? It may be helpful for those times when you are no where near a charging source, like at a ballgame, long plane trip, or on a job where you work in the field or where you can't be near a charging source, so there is a benefit to getting it but I still think the extended battery is a better choice for mobile use.
EDIT: I emailed tech support at New Trent and was confirmed that it should work for Thunderbolt with no problems. They also confirmed that the device does not need to be connected at all times to the phone, so it can charge up the phone and be disconneced from the phone. I think I am going to try it out and see if it's a good alternative to the extended battery.