If  you have every run out of battery power when flying, I have found this little backup/battery charger to be great.  I bought it on Amazon, but they are generally available.
http://www.amazon.com/SIIG-Portable-Battery-Charger-CE-CH0012-S1/dp/B0032ANC9Q/

Flying Tip
If you are using the new Moving Map feature you can "spin" the screen using 2 fingers and rotating. Very handy to get you location thoughts going in the proper direction.