I have an iPhone 4S and it would now be very, very difficult for me to dumb down to anything else. It's amazing and it has helped me tremendously with real world situations as well as being fun as hell. I use many features of it every single day that other phones simply don't have or don't do nearly as well (my previous smart phone's GPS system was a fucking joke, as was the 'map'). But the power and expandability of it is a big draw as well; I'm a gamer so I've got games like Infinity Blade II and N.O.V.A. 3 to keep me busy during long waits or if Diablo III's servers are down
. Overall, I couldn't be nearly as efficient as I am now without it. I'm not one to say "Oh, I couldn't live without it" because that's ridiculous, but it would indeed make my life a bit more convoluted and create more steps for me to take to get to where I'm going or get what I need. And a little bit more bored.
P.S. Jailbroken iPhone is fundamentally different than one sitting in a prison cell. This thing has potential that Apple, for whatever reason (HMMMM $$$) doesn't unlock normally. So that's a big factor as well. It's just so much fun, but it also happens to be very applicable to things I do daily. I don't know if I'm just a massive geek and have spent way too much time unlocking certain features but it seems weird to me that so many people here are of the mindset that it's not really helpful. Then again I'm out a lot and in need of computer access but can't bring my laptop with me (mainly I'm thinking of when I go into refineries when needed) so the prison-free-iPhone is perfect for me.
I also like the fact that I can stream porn.