I pulled my plugs at 109K miles. I think they looked similar to the ones above (judge for yourself). Frankly, I think they looked awful. A large part of the center electrode was gone. The car also runs considerably better. I can't speak to the gas mileage yet and my current gas mileage is pretty good - low 30's most of the time (mixed driving). Normally I get mid to upper 30's on the road. The gas mileage seems incredibly sensitive to every MPH you add - 63 MPH is great, 72 MPH sucks. The off-throttle response is so significantly different, I feel like I need to get used to the "new feel". Wow! Change your plugs if you have anywhere near 100K miles!
I used anti-seize on the plugs when I installed them. It kinda scared me pulling them.
I made sure the engine was cool - I've read that pulling plugs with aluminum heads and a hot engine is an invitation to tearing out threads. I set a box fan down on the motor for 20 minutes and the engine went from very hot to cool to the touch.
I was also very careful to keep the extension aligned in the center of the hole and applied force in a smooth "application".
I also blew the holes out with compressed air using a 10 inch tube to avoid getting debris in the combustion chamber. Lots of crap came out of the hole. I made sure to do this after I loosened the plugs.