Quark was a much more interesting character when all the Ferengi weren't around. He became a bit of a charicature whenever the family and co. were in town.
When I watched the show first run, I liked the episodes generally. Having rewatched the series a couple of times though, I find about half of the Ferengi episodes tolerable, whilst the other half range from average to bottom-of-the-barrel. Emperor's New Cloak, Profit and Lace, Prophet Motive, Ferengi Love Songs, Family Business, Rules of Aquisition can all go away.
Business as Usual, Body Parts, Little Green Men and The Magnificent Ferengi are the best ones, IMO.