i have also been experiencing the rough idle for a few months now and i was hoping someone here had it figured out.
i took my car into a dealership over turkey day weekend and reported problems with rough idling, decrease in gas mileage, and loss of "zip" or "oomph" when i step on accel pedal - basically i said it doesnt feel like the car is running as well as it was 6 months ago.
they found nothing wrong after test driving it.
the explanation i was given was the changeover from summer to winter gas (i am in chicago) that will cause rougher idles, decrease in mpg, decrease in performance... i said that sucks....
also, i paid for my first tune up 2 months ago at 25,000 miles and they replaced the spark plugs and air filter.