I picked up this book partly to continue studying communicating sequential processes after I'd read Tony Hoare's book and some of Dijkstra's EWDs. The book itself is well-written, is entertaining, and follows a logical order. It deserves a special place on my bookshelf.
On the other hand, after reading this book, I'm not so impressed by Occam2 the language. It may well be that Occam-pi solves my complaints; I still need to find out. Other than that, the best bet appears to be Google's Go language or the portion of Intel's TBB library that covers message passing.
Regardless, many of the concepts from Programming in Occam can be applied to other languages. This book will have an effect on my coding, even though I doubt I'll do any thing in Occam.