Got around to it a few weeks ago (July 23rd)... Bought NGK Iriduim IX or something like that. I honestly can not tell a difference. My plugs were the originals with 89K miles on them (NGK and Denso's).
Gas mileage has been relatively the same (the very high and very low MPG is when I stopped monitoring gas mileage and restarted.)
If you didn't disconnect the battery when you changed them out you might not see any difference for a while. Give the computer time to re-learn the engine. If you're looking for MPG gains from maintenance at that mileage, it's worth checking your air filter and throttle body as well as I saw some improvements after cleaning mine out.