When one of my rotors was fouled with hydraulic fluid I upgraded both to Ultegra. They work very well and the center lock design makes them very easy to install with just a cassette tool and chain whip.
Love the new design. Performance is excellent. No complaints. Maybe slightly less aero from the side? Seems like the old design had more cutouts that might catch crosswinds less... but I have no scientific date to back this up.