The Apple iPhone 4S might be a small upgrade if you were using
the iPhone 4, but it is a huge upgrade if you are upgrading from the
iPhone 3GS, as I was. Not only was the screen much sharper (albeit
still the same size!), the iPhone 4S was much faster. Unfortunately, I
also immediately noticed a big problem with the iPhone 4S - its
terrible battery life.
Recently, my brother pointed me to a very nice app called System
Monitor with Battery Max. It's a 99 cent app that allows you to
monitor the hardware and software of your iDevice. What's really nifty
about it was it was able to give me a live read of the iPhone 4S' CPU
load. What we found shocked us - the Apple iPhone 4S had a constantly
high CPU load even when it idles!
Read more at TechARP.