Energizer's AP1201 has been shipping for about a month, but one just showed up in the mail, so we thought we should give it a little ink because it's pretty nice.
The first thing to note about it is that it's relatively lightweight and thin but packs in a rechargeable battery and seems to offer good protection. We also liked the feel of the case, which is made partly out of hard plastic and partly out of recycled silicon rubber. While Energizer serves up a bunch of statistics on how much extra battery life it gives you (7 hours extra video and Internet time, as well as 4.8 extra hours of talk time on a 3G network), the basic idea is that it nearly doubles the iPhone 4's battery life.
The AP1201 recharges via Micro-USB (a cable is included) and you can either opt for a quick-charging mode that juices up your iPhone first, then the case, or get simultaneous pass-through charging of the iPhone and the case. Energizer says the AP201, which carries a list price of $69.99, can be recharged up to 500 times.