I have in fact tried this, 3 times. First was with a girl my own age (mid 20's) and I thought it was incredible. The next two times were with two different women both in their 40's. I must say, the older women absolutely rocked my world. The experience they brought to the bedroom and their sex drive just pushed the experience over the top. I also found the older women took a more motherly approach. They didn't just want to put it in my ass and pump until I came. They wanted to make sure they took their time, so we both enjoyed the experience.
I guess its no longer a fantasy of mine having done it and I will certainly be doing it again.