It's really quite simple. You have engineers and designers. Do not let engineers design a GUI.
I can partially agree with that. If your designers eat and breathe what works and what doesn't, works with users every day, reads past studies on HI design, that makes sense. The software engineers don't--they eat and breathe design patterns, libraries, revision control, debuggers, etc.. I can see software engineers getting cocky and thinking designers who don't do a lick of code don't know what they're talking about.
On the other hand, though, the designer doesn't really need an intuitive interface--he already knows how it works. He designed it. The software engineer doesn't need it either--he wrote it. In that regard, they're really both equally unqualified.