Its not going to be like you put on a turbo or something, but there should be some improvement.
If you reset the ECU when you install the K&N, you may see some difference. If not resetting, it may take some time. Since it comes pre-oiled, you won't probably have to worry about oiling for 15,000 to 30,000 miles anyway. :D
The trick to cleaning and oiling is to just spray the filter oil on, then let the filter sit overnight. If there are any white spots, touch them up. Just be patient, and let the oil soak in, then wipe off any excess or droplets. While waiting for the filter oil to migrate, use a standard filter in the car if you need to drive it in the meantime. Anyone that's had problems probably got in a hurry and soaked the filter and then stuck it right back in and drove.