I am happy with the iPhone as is for now. The Apps in the App store keep improving and making the iPhone better, IMHO.
I have thought about JB but have not yet. I do not mind "tweeking" things but I do not really have the time now to "tweek". I am hoping that the next major firmware update
(3.0 or whatever) will take care of some of the thigs I would like to see. If it does not add some features I may look at JB then ,but for now I am very happy with what I have now.