I've read it and it's very thought-provoking.
My only problem with it (speaking as an educator) is that Kohn assumes that children are just blank slates, and that they come unspoilt into schools and society. Sadly, that is not true.
He's right that chidlren are born with intrinsic motivation to learn and so don't need reward systems, but many children have lost that intrinsic motivation by the age of three or four - they need stickers, star charts and PRAISE PRAISE PRAISE just to function.
Personally, I think that the praise thing is a big problem in US society - the sort of inane 'good job' that is constantly said to children without any clarification about what, if anything, is good about the job that they did. Kohn has a really good point about praise - it's like a sugary sweet that adults offer children to make them feel good for a few minutes, but it totally lacks nutritional value for the soul.
I try really hard to be specific to children and not praise them - eg 'I noticed how carefully you stacked the bricks' not 'Wow! Great! Good job!'
I'd recommend reading it, but it's not a book I particularly refer back to - once you've read it, you 'get' his message, so I'd recommend the library, or get a copy second-hand.
Hope this helps!