IPhone functionality once contract expires?

I have a first generation iPhone which is not jailbroken. My 2 year contract with AT&T runs out next month. If I cancel my service plan, will I wind up with an iBrick or will I still be able to use it like an iPod Touch?

Anyone have any experience with this? Serious answers only, please.

I’m interested in knowing specifically which, if any, functions
(notes, apps already installed, wi-fi surfing, iPod, camera, etc.) will still work. Would jailbraking it change this outcome in any way?