Feature:
The big thing it lacks is dedicated line output jacks. There is only a stereo headphone/output jack. I was also very disappointed to discover that 100 of the 676 advertised "voices" are available only if you control it from a computer.

Quality:
I have not had the MU15 very long, but it looks like an average Walkman as far as constructiona and quality. I suspect that many of the controls will stop working after a year of repeated use. The volume control is a tiny slider - that is really ridiculous.

Value:
It is definitely worth the price I paid for it, and its lower price matches its somewhat limited features.

Desirability:
It is fun, and sounds good, but it is not a professional tool.

Sound:
All the sounds are good, though a lot of the voices are just minor alterations to basic sounds like piano, saxophone or whatever.

Overall:
This fills my current needs, for a basic multi-timbral, polyphonic sound module with a variety of sounds, and it is helping me learn how to use my various MIDI equipment. I will definitely buy another product sometime in the next two years that is larger and more pro-oriented.