I have the Tumi 2200mah with wireless charging mounted in my car as a sort of "car dock+ charger", and keep the TurboPower 3490mah on my phone most of the rest of the time. With heavy usage it makes it a good two solid days, and being able to charge both the phone and the mod at the same time (on different chargers) means that I could be ready for another two days in less than 2 hours. I HIGHLY recommend a battery mod.
I also picked up the gamepad mod when it was "buy a mod, get the projector free" sale at Verizon. It's nice for some games, but not everything plays perfectly well with it. It's well built and is MUCH more responsive than even the xbox controller paired via bluetooth.
The projector, well, it's pretty cool, even at only 480p. It'll get much more use when it gets warm out and I can do movie nights in the yard with the kids!