I'm not doing it, but I read a bit about it and I think it is a great idea.
The reason I don't follow it is I love eggs too much, and have found it difficult to live without them.
I tried to do vegan with my nephew while he was visiting us a few summers ago. I had a difficult time w/out eggs, and skipping the half-and-half in my coffee and cream in my tea.
I like Bittman's approach because of the flexibility. I've found, for me, that general approach yields the most success, and is easier to maintain the results over time.