Rob W. said it better than I could. I would add, however, that they don't have the "ring" of roundwounds. It's really a very different sound. And, fortunately, the brightness of the TI's wears off after a few weeks, and then they sound really great

. IME, the Rotosounds sound closer to rounds than other flats do. Probably why I don't like 'em. If you want to know what old flats played with a pick sound like, listen to "Horse With No Name", "Tin Man", and others by America, and you'll hear Joe Osborn mixed up pretty loud.