I recently made the switch from Android to the iPhone 4S as my daily workhorse smartphone. I've been using iOS devices for years, so I'm familiar with all the apps (because they're already running on my iPod touch and iPad).
After using the iPhone 4S for a few days, I've concluded that I need to get a battery case. The built-in 1,432mAh battery in my iPhone 4S doesn't provide enough power for my type of use and there is no option for a removable or extended battery on the iPhone. I'm frequently using the built-in GPS, taking photos and videos, and doing a lot of uploading/downloading (since I still have unlimited data on Verizon).
So, now I'm on the mission to test a few of the battery cases made for the iPhone 4S. Some are bulkier than others and I don't need the one with the largest battery. So, stay tuned as I give these a spin.