The panel K&N will breath a alot better than the standard, and as the surface area of the panel becomes blocked the air will still be able to flow thru a lesser clear surface area, supplying enuff air to keep you going, but, no, you won't really feel a power difference, they are simply designed to allow a greater airflow, but at the end of the day, that flow is only what you engine will require, no more.
The big plus is as HG says, you can clean it on the go, and thats a big plus when your outback and get caught following a roadtrain or drive thru a dust storm, not many jeep parts shops in the desert!!! And the amount of times you can just clean and re-oil the filter will equate to quite a significant cost saving over the life of the filter.
Quick tip, don't throw away your old filter, you can use it as a spare when you are cleaning and drying the K&N, pop in your old one to keep driving