Definitely, all over.
It really seems to wake it up all throughout the power range and you can really hear the motor a lot better...my brother thought I changed the exhaust, its that noticable.
As far as top end power, it has to help...its like running an open TB and I would imagine combined with exhaust it would really run well.
I know one guy said he was doing 66 mph flat ground, sitting up with the KN and an exhaust system.
Cruising today with a 13t and just the KN my bike was doing 70-71 which is probably 63-64 mph cruising speed with that gear i have in there.