I think this is increasingly common, as more guys are hearing about the idea and, feeling more comfortable with their own sexuality, thinking that they'd actually quite like it!
Some guys, of course, are still to masculine and uptight to even think that they might like something in their ass - that's only for fags! - but as more and more are relaxed about these things, and the quality of the toys improves (feeldoes... mmmmm) the whole idea of role reversal is spreading.
I for one love it, and so does my bf. He likes the physical pleasure and chance to see me in a different role. Yes, the motion can feel great for me too, especially with a feeldoe, which instead of a strap is simply held in place by inserting one curved end into your vagina. Otherwise most pleasure is derived from the domination aspect and knowing that I'm pleasing him. I like the new role, the chance to 'return the favour' if you like lol, to know how he feels when he's fucking me, and the look on his face when I get into my rhythm is something else - again, I guess I now know how he feels looking at me!
If you hadn't already guessed, I heartily recommend it!!