Short version: skip this digital version and stick with the print edition.
When it worked, TrailRunnerMagazine was okay. My main issue was the extremely poor quality of the images. The magazine was readable, but the images were extremely over-compressed (or something), and so very pixelated. A pity on a retina display (even a standard one, for that matter).
Then...TrailRunnerMagazine crashed, I had to reinstall and was unable to restore my purchases. There's a button to do that, but it doesn't actually do anything. Messages to customer support have gone unanswered. Terrible terrible terrible.
So now I have a paid subscription that I can't do anything with. I'll likely send Apple a note as we'll to see if that does any good, but it makes me sad that such a good magazine would have affiliated themselves with such a HORRIBLE digital magazine provider.