Just a "closer" post for those who didn't read the review.
The O-Max was a bit painful at first. I wasn't exactly sure how to use it, and made a few mistakes. Go slow and carefully if you're trying out the O-Max so you can figure out how it works with your internal anatomy, and don't worry about getting the middle ball inside - that might come, or it might not, and the toy works OK with the ball either inside or outside. Most of my painful moments came from trying too hard to get that middle ball inside...
Now that I have both the O-Max and my body figured out better it isn't painful, and the O-Max delivers sensations very different from the other prostate massagers I've tried. There are many muscles down there, and the O-Max is able to pick up movement from a number of them. It's still a very intense toy, though, so keep that in mind.