i've got around 9300 on mine and it seems like the mpg have improved a little... i use to average 16.5 mostly city and now getting 17.2... same daily route to work.
also, I did change back to a paper filter vice the k&n I had been running, so maybe the k&n wasn't helping out that much

 

You should see your mileage improve after 4 or 5k miles.

 

The trend I have seen from posts is that it improves with engine break in, and then declines as people bolt a bunch of weight on.