I have both this one and the cheaper model that they sell. This one is much better. It has a larger capacity than the internal battery, so you get more than 1 full charge. It's kind of cumbersome to use the phone with the battery pack plugged in, but this is the case with all battery dongles like this. It does stay plugged in pretty well though. That's one thing I cannot say about the cheaper one.
I see they have dropped the price to about $10 now. I paid $14 for mine. Thanks for the tip I think I will buy another before my vacation.
Yeah their not bad, if I'm gaming on my iphone like all day then I'll pop it on when I'm not using the phone, I also use an Energizer battery pack, kinda like a 4/5ths case, also good. It's only $10 give it a try.