content: There's an unofficial app store for iPhones called Cydia (I think?).  I believe you can change the overall style or theme of the interface, it's tougher to use other apps as defaults (like web browsers and such) without jailbreaking, and if jailbroken, you have more access as a poweruser to fiddle with the inner workings of the operating system and file structure.  I'm sure there is a lot more, but I've never been an iOS user, so maybe someone else can shed more light on other useful benefits.