I am also using the power skin, and I thought I would throw in my two cents as well. The extra power is nice, that's the big reason to buy one of these. However, (contrary to what the man at the ATT store said when he sold it to me) you can not connect your phone to the computer while the case is on. Charging is done through an identical port on the side of the phone, but if you try to connect to your computer, it will charge but you cannot sync files. This is not a problem if you sync wirelessly or via the cloud, but just a heads up.
Another big thing to be aware of is that as the battery pack gets close to empty, it will switch the pack on and off as it shakes the last couple drops of juice out. This amounts to continuous "phone plugged in," and "phone unplugged" notifications for a couple minutes. This actually uses up a noticeable amount of battery power because it has to turn the screen on each time. @davidgoerndt66 You didn't mention this so I don't know if you have the same issue, but if you found a way to avoid this let me know.
Anyway, I don't mean to discourage anyone from getting the case. I continue to use mine. These are just things I wish I had known before I bought it and might help you with your decision.