The reverse lens actually functions as a high powered close up lens. A 50mm reversed lens is said to be up to a +20 dioptre. The Raynox 250 is a +8.
So the higher the dioptre, the shallower the DOF, the closer the working distance, and the harder to manage.
I have used the reverse 50mm F1.7 on my FZ10 before, and though I can get some shots of it only at abt x8 and not more, I find it too difficult to use. The DOF is too shallow, and the working distance is 4cm.
For Raynox 250, you can see most of my macro pics in the Macro forum or in my gallery macro or latest pics of the mtn gallery.