An interesting idea, but I think that some sort of solution where you could not only keep a copy of Wikipedia in your pocket, but get rolling updates to it every day/week/time_period would be nicer. Especially on an iPhone/iPod Touch, with the wi-fi or EDGE.
It would be nicer alright, but having used it for a while, I've found it doesn't make much difference. A Britannica edition used to last a decade; I can survive a few months without update.