BAD: I've just recently installed Porterfield R4S and I'm NOT impressed. Actually I'm quite disappointed, they're less dust but not nearly as effective as the OEM pads. With OEM pads, I could trigger the ABS system quite readily in spirited stops. With the R4S pads, it definitely takes abit more pedal pressure to trigger the ABS system.
UGLY: OEM pads seems to provide great short braking distance but with lots of ugly dust. It's a love-hate thing.