Nope, if you don't like it you can just restore from itunes and it's all back to normal. My iphone is super cool with jailbreak. I use an app that tracks me on google latitude when ever a significant change of location happens my phone updates and the people I want to have see my location can track me down. This app was rejected by the appstore because of the obvious security concerns with the general Apple population. I also have another app that lets me wireless sync to itunes with out having to plugin my cable.
Seriously try it out, do some research to find the most useful apps and I promise you will love it.
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Fell off the wagon....