I think he's right that if you want to be comfortable speaking in a language, you should start practicing that from the start, but that's not exactly a profound realization, and it's about where our agreement stops. I think he uses the word "fluent" too freely, and he comes off as a motivational speaker with fairly empty/generic/"just do it" advice. I stumbled upon his blog when I was looking for Thai resources; his Thai was terrible, and he said at one point he could read even though he couldn't read tones. Um, no. That's not even decoding, let alone reading. That made me doubt his self-proclaimed achievements from the get-go. 

Very little of his advice is specific to a language or original (possibly none). Basically, he's a motivational speaker selling himself, and his abrasive interactions with those who disagree with him or criticize him show how jealously he protects his brand. 

I'm not buying.

Here are my thoughts on Benny's book, which is essentially a reflection of his entire site:

http://polydog.org/index.php?threads/fluent-in-3-months-by-benny-lewis.17/page-2

Language learning is plenty of people selling you a revolutionary method to learn any language in a incredible short time and/or without effort. Maybe some of those are real enthusiasts trying to help, but most of them are just people selling something that will not make any good. I prefer not to trust any of them and keep studying.

If you want to know for real how much time can take to learn a language to an English speaker by attending a school at about 20 hours per week, take a look here: http://www.effectivelanguagelearning.com/language-guide/language-difficulty

If someone tells you that you can learn Chinese in a couple of months, just run.