Adrian, I ran this year. Despite struggling, I'm in again for 2015. The whole experience was superb.
As Jimbob said, the 1st half is almost too easy. I thought I had judged it well, and felt ok after Heartbreak Hill, but pushed too hard going down to Columbus Circle causing my legs to seize up. The final 5 miles turned into a painful slog! It was pretty warm, so that probably didn't help. I've been doing a lot more leg strength work since. Hopefully that will help.
I found the hill after the Charles River (16m) and the hill after the fire station turn to be the most difficult, most likely due to the change of terrain.
I ran this last year, No problems with the start. I got to the pens about 20 minutes before the start and got fairly close to the front. I could run the pace I wanted straight away(slower than Mr Cleasby and Joolska).
A couple of tips - avoid the breakfast run on Saturday, it was Borderline dangerous! The pasta party was good, excellent pasta and real beer.