The MPN is a noisy, stepped beast that can often be found on the cheap and is more than capable of delicious espresso.
Positive Product Points
easy to adjust
fairly easy to disassemble
easy to clean (after minor modifications)
low grounds retention
Negative Product Points
steps are a little too far apart for me
would not fit under cabinets with hopper installed (fits fine without it)
I purchased mine off eBay as a commercial pull. It was very dirty and required cleaning and new burrs before it could be used. Even without documentation, once cleaned it was fairly easy to install burrs. (This was my first grinder.)
Mine is easy to adjust. Simply press the pin down and turn the collar. The pin settles into one of the notches in the collar to hold the burrs in place. Unfortunately, the steps are farther apart than I'd like them to be. I see 4-6 seconds change in extraction time per step. On my machine, the steps are not numbered. As far as I'm concerned, this practically negates the value of a stepped grinder; it's not easy to return to a specific step without the numbers. I understand that some variants of the MPN have numbered steps.
This grinder is the loudest appliance of any kind in my house. Thankfully, it also only takes around 20s to grind ~18g of coffee. The noise is tolerable for durations this short.
Removing the two screws from the top of the doser made a huge difference in usability. With those out, it's a snap to brush out the chute and the doser sweeps very clean. If you're willing to sweep the chute with a brush after grinding, ground coffee retention on this machine is very low. I've measured it to be between 0.5 and 1g.
With the hopper installed, this would not be a reasonable grinder for my kitchen. Mine has no interlock that I'd need to defeat, though, and runs well without the hopper. I use it with the nylon tamper set on top of the throat to prevent popcorning. The throat holds more than 20g worth of beans.
All in all, I like this grinder. It's capable of very good espresso and I've gotten great service out of it. I wouldn't buy it again, though, because I've found that I prefer a stepless espresso-only grinder. Being a less popular model, it's easy to find on the cheap. If you can find a model that only needs new burrs, it can be a great value.