I had my first diaper experience a couple of months ago -- someone I met on BDSM,com. Her fantasy was being made to wear diapers, then be verbally humiliated by her "daddy." She lived close and was in the Navy, so we had enough time to dialog while she was deployed and we met when she got back.
The overall concept wasn't that much of a turn on at first, and I am a mellow do-no-harm kind of guy, so smacking her verbally was hard at first --- when we got into the play, I found diapering her a real turn on -- quite unexpected -- put baby powder on her and inspected her vagina and took her temp rectally ... part of her play was being made to pee in her diapers while I was scolding her - which she did - and I also found that to be a real turn on -- since I had to strip them off her and put new ones back on ....
She was not initially into enemas, however she was curious so since I was indulging her, she indulged me, So before I rediapered her, I gave her a punishment enema with a nice red bag ... while scolding her some more.
I let her get rid of it before I rediapered her then we dealt with the bulge in daddy's pants ...
We did this a couple of times -- she is deployed now for a few months and I Iook forward to her coming back. There is a sort of hypnotic feeling after putting on the diaper, seeing her there naked with the diapers, being 100% submissive and under my control. So, for us right now -- it's a daddy / daughter role play. It was really fun for both of us.