That answers my question then - on the 1440x900 13" MBAir, the black lettering from Practical Typography is jarring, and unpleasant to read for long periods of

That answers my question then - on the 1440x900 13" MBAir, the black lettering from Practical Typography is jarring, and unpleasant to read for long periods of time for me, but Medium flows very well - and I read tons of material on their site. PT is just very unwelcoming for me to read - both the diamonds all over the place (which reminds me of the PCL printout when you didn't have the correct font installed), and the assault on my eyes. Perhaps on a higher-resolution retina display it works out better (and perhaps Medium suffers somewhat in comparison)