Heres a picture of Eric Gagne throwing it, you can see it a little bit
And get a good idea of what it looks like. I would suggest giving it a go, it is an awesome pitch and I don't know why more people don't throw it. Because of the nature of the grip, it will have more movement than basicly any other changeup grip, and is not all that hard to throw either.
Just remember to
1-Keep up your fastball arm speed, otherwise you won't get the full splitter action as it comes to the plate
2-Keep your wrist loose, again to get the full extent of the splitter movement.
3-Keep the "Circle" made by your thumb and pointer finger small. This one I figured out myself, it needs to be small and only hold onto the ball a little bit, so that the pitch comes out of your hand easily. Otherwise, you won't get the same action.