When the costume department decided to make an effort with an alien culture, they regularly went for a clown look; eg the Ferengi and Neelix.
I quite liked the efforts they made for them, to be honest. Quarks suits (well, when they got away from the darker versions) always looked spot on for the character, and Neelix was the same. The right costume for the right guy.
The pajama look for uniforms didn't really bug me that much (though I only really thought that applied to Nog's cadet uniform) as I liked the logic of it being comfortable.