In reference to Guinness not having an aftertaste- taste is, indeed a subjective thing. Different people have different thresholds for various tastes and aromas -some are higher than other's. In the case of Guinness, however, given the fact that it is brewed with a very high dark roasted malt content, it is difficult to imagine it not having an aftertaste. Perhaps you are serving it too cold and may be stunting your palate's ability to perceive the full aftertaste. Traditionally Guinness is served at 55 degrees fahrenheit. Cheers!