I finished W1D1 tonight, and I'm on my way. As someone who really hasn't done much exercise in a long time, am I the only one who thought I was going to die right around the 3rd set? I managed to break through it, but man, it was killing me.
I have to disagree about the ball of the foot landings. Having read around the intarwebs to find out the best way to run, I've read that the best way is whatever is natural to you - heel first (the majority of people do this), center, or balls of your feet (very few people do this, except when sprinting, and it will contribute to exhaustion if done for long). Don't force yourself to run in a way that's not natural. Don't exaggerate your arm movements. Keep good posture and keep your hands relaxed. (most of this you probably knew, but since most of us here are new to running, it's good info to remember and put out there)
Anyway, I'm ready for day 2 on Friday, but I sure hope it gets a little easier than today.
Good job to everyone else who is working on this, and your great progress! It makes me think I can do it, reading your posts.