When I first got the mono machine I tried playing it like a traditional synth making traditional patches Ect. In that case, I do agree it sounds rather weak and bland. However once you get a great melody going and start using Plocks and slides you realize the potential of this unique piece of gear.
The key to the MnM is the the Sequencer is an integral part of sound designing process. I can see allot of situations where the MnM might not fit in. However for me in my out of the box set up it has changed everything for the better. Most of my songs use all 6 internal slots and 6 ext midi channels.
Of course I use allot other synths as well as the MnM internal synths, but you could make a great song on the MnM alone. It really is a song writing power house, combine it with a few samplers and multi track recording in your DAW of choice and you are on your way.