I upgraded my iPhone 4S last night to iOS 7, expecting there would certainly be some trouble with apps that stopped working or the interface would be too new and different. Instead, it went completely smoothly and was a non-event. iOS 7 has some handy new features and seems significantly faster than iOS 6.
Some have reported more battery usage with iOS 7. I use a Mophie battery pack on my iPhone so that’s not an issue for me. I also turn auto-brightness off and keep the brightness on the low side and only have about ten apps that push notifications to me, which helps save battery life.
Have you upgraded to iOS 7?