I jailbreak all of my devices. Not only does jailbreaking allow you to customize your device in many awesome ways which Apple does not allow, but there are also some things jailbreaking provides you with the option to do, which make you more productive while on your device. It is also just plain fun having all the options jailbreaking gives you.

For me, the must have things you can get from jailbreaking, are SBSettings, Winterboard, Five Icon Springboard/dock, Mobile Terminal, and Lock Info. These are all things I think are needed on every Apple device, jailbroken, and nonjailbroken.