For me it was a very specifici experience: As a male, my wife and I are mates. Tina and my wife are completely platonic girlfriends. There is no sexual energy there for Tina.
However, dressing...especially dressing to the nines...is sensual. There is a difference, but the biological function can always see the difference in the beginning, so there is a physiological response, or at least the start of one. It doesn't go anywhere, but there is a certain stimulation for a guy who is used to boring guy clothes to suddenly find his body encased in stockings and satin!
So, I would say there is probably always a sensual response, not necessarily a sexual response to crossdressing. At least that was my experience.
