I haven't managed to successfully WILD, but at least twice in my life I think I've approached that void.

The first time was in high school when someone was leading our band through a visualization exercise (and a rather lengthy one at that). He was bringing us into a very relaxed state, further and further down, and at one point I approached what I believe was almost a hypnotized state. Unforunately I jerked away from it slightly and just about ruined everything that he had been having us do (for myself personally).

The second one was when I was listening to an HILD mp3 and one time I approached that void again, but just before I fell into it I jerked. I guess I just don't trust the speakers enough... maybe if someone I trusted a lot tried...

That's been my experience, though. Hopefully I can learn to relax.