I used to have a 3gs as my old phone, after moving to the iphone line of products i have never found anything else as functional since. I know own a 4gs however i only upgraded because i wanted more memory so that i could use my phone like an ipod classic and carry my entire library around. The battery life, like all smart phones, is not great but if you charge it every night it will last all day without worry. It only takes a couple of hours to charge and can be charged via mains or your mac/pc. What you see on the image shows the basic apps that come bundled with the phone, these include ipod, email, web browser (safari), camera, calender and so on. The camera is not great at only 1.3mp but it does the job for those nights out when you dont have a different digital camera with you.
The iphone can play back videos but they have to be in the right format to do so which can be a tad annoying formatting your movies. Itunes does include a "create ipod version" function though so this is not exactly difficult, just time consuming.
The phone also includes gps chip, and a gyroscope which can be used with different apps.