I loved it and saw good results (dropped about 7kg in 3 months). After that initial three months I relaxed it a bit--my cheat day became more like a day & a half, I had alcohol a few days a week--and only regained less than a kg.
I've just read a book called "Why Are We Fat?" by Gary Taubes and his hypothesis (which is very persuasive) aligns with Ferriss' Slow Carb approach really well. I've been on intermittent fasting for the last four weeks and am going back to Slow Carb.