I did my own modifications but followed the basic principles to "sharpen" my running after a winter of "slow" runs that I used as a foundation. I qualified for Boston using that program and was continuing to improve until I suffered a stress fracture. I see it as a risk and reward type of program. You may be able to run less but it will be very hard and it will be hard on your body - why there are the rest days that they have and the low impact training.
I followed the philosophy for a couple of years after that: qualified for Boston again, won the season age category in some shorter trail races and finished top three and would have sworn by the program but when the wheels fell off, I did virtually no running for about a year.
Now that I am back on the marathon track, I am running more miles but much slower. My only speed work is to throw in a 15 K "marathon pace" - very conservative estimate with the predictors telling me I could run a 3:35 but the marathon pace is based upon a 4:00 marathon and I can report no injuries thus far. The running is a lot more enjoyable as I no longer panic when I hit a light or if I have gone too fast, I will take a walk break to lower the heart rate. It is also more enjoyable to see the environment around me rather than being fixated on my watch too see the pace I am running and the pavement 10 feet in front of me.
I suppose what I am saying is that from my personal experience, if you have a limited amount of time and do not mind pounding your body, the run less program [Furman First] can get results. But it seems to me that in exchange, one risks a greater chance of injury.
I should I that I still do weights. For me, weights seem to strengthen the core, etc and help me ward off injuries. Plus, a nasty and cold day, a little tired and sore, nothing wrong with 30-45 minutes on a elliptical instead. Listen to your body and be flexible cannot hurt.
We runners are all a little nutty, but we're good people who just want to enjoy our healthy, primitive challenge. Others may not understand running, but we do, and we cherish it. That's our only message.
- John J. Kelley