Picked up the Phonesuit Mili power pack iPhone battery last week. So far I am happy with it. The look and feel is like that of the iPhone plastics. It also has a few color combination's to choose from. Black and White base colors for your iphone color. The battery itself is pretty amazing, I can now charge my iPhone + Mili at night, leave for work at 8am and come home at 7pm with still 2 mili bars left and a fully charged iphone. Before the mili, the iPhone wouldn't even last me till the ride home unless i was charging it at my desk during the day.
Here's some reviews:
planet-iphones
Gear Diary
And the link
MiLi
Here's some reviews:
planet-iphones
Gear Diary
And the link
MiLi