Sure, the iPhone is 'fine' all on its own; however, there are many useful tweaks and implementations to the OS that Apple simply refuses to do. I personally enjoy having a jailbroken phone because I'm able to increase the functionality of my device, as well as personalize much more. You don't have to go crazy and make your home screen do flips when you turn it on, but there are certainly many non-gimmicky and ethical uses for jailbreaking that can greatly enhance your experience with your phone. Personally, I like being able to hide or put in a folder apps (such as newsstand) that I don't use, and removing limitations such as 12 apps per folder. The fact that I have to open the settings app to adjust things such as brightness is very annoying, so SB settings, or the incorporation of such in IntelliscreenX (recommend) is a great interface enhancement.