In reply to Plyometrics: have you done it (Boston)? I did it in, I think, 95. I didn't run very well, but the course the course is amazing. The first part is through New England in the spring, colorful houses, not a very big road, very green, decent supportive crowds. This part is supposedly downhill but is gently undulating.
Once you go by Wellesley college and especially after the Fire Station the road opens and the crowds are huge! Also it got hot, but the hill seemed very ok.
I can't think of a course to compare it to in all honesty. It is very special as it's not only a fantastic course, but so much history has been run on it (eg Beardsley/Salazar )