From personal experience, and since I have only tried it once, I have to say that I somewhat liked it based on the feeling, although she wasn't too thrilled. There was the initial awkwardness of trying to get it in. It does take a lot of lube an still there is an bit of fumbling around to get beyond the threshold. Also when you do push in and pass the initial threshold you might end up sliding all the way in very quickly. That's what I did. It was hard to push in at first, but I ended up slamming her head into the wall (totally by accident) because when I finally made it in it was really smooth and the force that I used to get inside her made me end up pushing her forward. Before we started I was excited to try it because it was something new, and different but it really didn't live up to what I thought it would be. I tended to get stuck a lot and had to re-apply more lube.
I probably need more experience to make a more qualified judgment though) but after that first time I have not been too excited to try it again! Also, its never a good idea to switch holes because taking it out of her butt and putting it in her vagina can possibly cause bacterial infections for the girl so I ended up pulling out and going to wash myself in the shower/toilet that the girls have and then returning for regular sex. (To the best of my knowledge switching holes can cause infections, but then I am not a doctor). I just don't want any of these girls to have an infection based on my actions.
I suggest that you try it at least once and see for yourself. I certainly can't disagree that it makes some very happy. Look at Smilybob1's post. He makes me think that I might want to try it again someday!
