I didn't mention it, but I dipped my toe in the hill sprint water a couple of days ago, doing a whopping 2 hill sprints lasting ~ 10 secs each. Hudson recommends starting with 2 and adding a couple until you get to 10 (20 for middle distance runners). He also recommends starting with a 6-8% grade, which I did, instead of jumping into 10 hill sprints on a 15%(!) grade. I did 4 this morning and it felt good. When I was doing Rubio's 3 x (form, 3k effort, sprint; ~60s each), I was always felt the beginning of the sprint was the most beneficial. Now that's all I'm doing :-)
Of course, I registered for the 10k and the weather took a turn for the worse. It's supposed to be 68 at 8am, which is about 20 degrees higher than ideal for me, and 10 degrees higher than predicted when I signed up yesterday. It's also the warmest, I believe, since the day after the ridiculously hot/humid half I did a week and a half ago. Still, the dew pt should be below 60.