Here's a YouTube review from Larry Greenburg:
YouTube - MiLi Power Pack
And here's the different specs based off of the data from their sites:
Specs For MILi Power Skin:
Product Dimensions: ???
Battery Capacity: 1300 mAh
Estimated Shipping Weight: 0.5 lb
Capacity 1200mAH
Standby Time Up to 230 Hours
Talk Time Up to 3.9 hours on 3G
Internet Use Up to 3.9 hours on 3G
Audio Play Up to 19 hours
Video Play Up to 5.4 hours
Specs For morphie juice pack air:
Product Dimensions: 4.90 in x 2.59 in x 0.75 in; 2.66 oz
Battery Capacity: 1200 mAh
Estimated Shipping Weight: 1 lbs
iPhone 3GS:
Standby Time: Up to 270 hours
Talk Time: Up to 4.5 hours on 3G | Up to 10 hours on 2G
Internet Use: Up to 4.5 hours on 3G | Up to 8 hours on Wi-Fi
Audio Playback: Up to 27 hours
Video Playback: Up to 9 hours
iPhone 3G:
Standby Time: Up to 270 hours
Talk Time: Up to 4.5 hours on 3G | Up to 9 hours on 2G
Internet Use: Up to 4.5 hours on 3G | Up to 5.4 hours on Wi-Fi
Audio Playback: Up to 20 hours
Video Playback: Up to 6 hours