I use both (model M at home, Unicomp at work) and while I've not had any failures, it's clear that the Unicomp is made of cheaper materials. One example is the case itself - the Model M's case is made of thick ABS, while the Unicomp is made of thin polystyrene. As a result, the two keyboards feel different - there's a a resonance from keypresses on the Unicomp that's almost entirely dampened on the M.