The Milkbox does not have a dust cover for the headphone jack. The Milkbox I bought worked for about 2 1/2 weeks...then it stopped. My mophie is now on its way. Do not buy the Milkbox. I learned my lesson.
Has anyone heard of the Milkbox charging case for iPhone 4/4s? It is half the price and seems very similar to the Juice Pack Plus but I can't find any reviews.
I have the Milkbox on my iPhone 4S. I got it for 54 bucks. It's pretty solid. I let my battery go down to about 20%, I turned on the Milkbox and it charged it to 65%. I was using the phone the whole time it charged. I know a couple of people with Mophies. It's probably not as good, but for the price of the Milkbox, it is definitely worth it. I think the only con about it is that you can't charge the case and the phone at the same time. It's not that big of a deal.