Moi. Having bad luck with them though :/ I got the white Mophie air to go with my white 4S, cos I just couldn't deal with the bad battery (waiting on a fix from Apple in the next few weeks before I try swapping phones). The first one chipped like a mofo - just putting it on and taking it off once I had several bad chips on the front inside lip - it's like everytime I put the case on, it scraped more white paint off, and it was black underneath. I tried to just keep the case on, but a week later I needed to take it off, and again, major chippage. It was starting to look like crap, which is unacceptable - my bf's employee has had one for ages and it doesnt look like that, so I returned it yesterday.
Now the new one, the bottom part won't click in securely - if I merely bump it or hold it wrong it'll slide off. *sigh* back to the Apple store...
The battery power itself tho is great, from ten percent left on my phone, when I turn on my Mophie, even with some usage I can get up to 85-90%. Good enough for me.