Just about perfect
MMR is a perfect puzzle video game. It teases your brain as well as your hands, requiring you to figure out what to do and then pull of the precise motions to do it. It takes full advantage of the Wii remote to make a control scheme that is completely intuitive and very responsive. It's got plenty of length and re-playability to make it a good value. It graphics are simple but very effective, and the physics of the mercury blob are both cool to watch and fun to use.
The most impressive thing about MMR, though, is the artistic purity of it. Ignition took a very simply concept and milked it for all it was worth, using creativity to expand on their basic idea and make it something that's fun to play for many hours. I wish more developers would put this kind of thought into their games.
My only complaint is that some of the levels are simply obstacle courses and not really puzzles. A puzzle game should always consist of more than simply getting from A to B without falling off the edge. Those levels are the minority, though, and there are enough total levels that they can mostly be overlooked.