I did the full yesterday, my first marathon and found the constant up and down of the underpasses quite hard work, but was a nice event and well organised. Managed to get a GFA time which will get me into London next year.
I found Julian's book invaluable in my quest to run faster 5/10Ks, I particularly wanted to run a sub 40 10K which I managed to achieve in Richmond yesterday. I ran a similar course 2 years ago and did a 51:25. Doing the types of sessions mentioned in the book has made a world of difference. I do other training (for Triathlon) but only do 3 (very occasionally 4) run sessions a week, its definately a case of quality over quantity.