Just did this for the first time last night... I was sleeping a friend's guest bedroom and thought momentarily that I had wet dreamed in his sheets. I checked my actual body from within the dream though (just felt it but without waking up) and knew I hadn't. Wow did it feel amazing though! Arguably better than the real thing but with no mess! I lasted but 30 seconds in the dream too

I personally found this mental ejaculation amazing... like it really had me convinced that I had actually ejaculated. What a trip... I mean I'm not surprised, the world of Lucid Dreaming is full awesomeness.