I installed my K&N CAI very soon after getting my jeep. I will echo what Salvador has said...no huge difference, but a I think a slight upgrade in MPG. For me, on a 600 mile trip, I averaged 75mph and 29.5 MPG. As somewhat of a side note, I hear people talking about MPG all the time, but don't state their average speed. That makes all the difference in the world. Once you exceed 65MPH your fuel economy really starts to drop (I find that the case on pretty much every vehicle I've ever owned). At 65 MPH, I'm sure I'd be at least in the mid 30's on MPG if not better.
I didn't test my 0-60 prior to the CAI, but when I did test it recently, I'm hitting 60 MPH in the very low 7's.
I also have an after market exhaust and plug and play Banks Bullet tune (soon to be removed for a true tune from HD Diesel Supply in Canda).