I have one and like it quite a bit. I have found that when pushing the limits of gravity on it (for a 5 gallon batch), the mash can get stuck because of the amount of grain in the pipe vs water. I recommend a brew bag to help with this, since it will channel all around during runoff, not just the bottom of the pipe.
I have also done a few batches that were bigger beers. I used the M+B to heat my mash water and actually mashed in a cooler for space, then returned the runoff to the M+B for boil (no sparge). It has its limitations on batch size and gravity, but it is a well made and handy little unit. If you are making 3-4 gallon batches it is a REALLY handy solution for space and equipment saving.