Is /dev/random strong or just good?

Guy Rutenberg have written a little C++ class that provides random numbers on *nix platforms and he has published it on his Blog under a MIT license. The class used /dev/random and /dev/urandom to read random numbers provided by the kernel. He claims that the provided numbers are strong, even cryptographically so. I once read that "self-made" cryptography should always be avoided. This case, however, is a mix between a self-made and a ready-made, since the kernel provided random numbers are used. So, the question on security boils down to a simple question:

Is /dev/random cryptographically strong or just good?

I would like to have all the links you can provide on the matter. :-)

"Assembly Language Step by Step" by Jeff Duntemann.

I have been reading the book "Assembly Language Step by Step" by Jeff Duntemann and I would like to say something about it. Historically, I have been more of a high-level kind of programmer without any particular interest in those lower-level things like "MOV", "EBX" and "REP STOSW". Most of my work have been performed with C++, PHP, Perl and such languages.
Some text from the Back Cover: The bestselling guide to assembly language–now updated and expanded to include coverage of Linux. This new edition of the bestselling guide to assembly programming now covers DOS and Linux! The Second Edition begins with a highly accessible overview of the internal operations of the Intel-based PC and systematically covers all the steps involved in writing, testing, and debugging assembly programs. Expert author Jeff Duntemann then presents working example programs for both the DOS and Linux operating systems using the popular free assembler NASM. He also includes valuable information on how to use procedures and macros, plus rare explanations of assembly-level coding for Linux, all of which combine to offer a comprehensive look at the complexities of assembly programming for Intel processors.
I hade litte to no experience with Assembly programming before reading this book and was searching for a good entry-level introduction. This book was recommended somewhere so I gave it a try. The book begins with an introduction to the binary and hexadecimal bases used, followed by information on the memory space available on x86 CPU's and how the memory is organized (e.g., real mode segmented model, protected mode flat model). Some nice chapters regarding string handling followed by coding Assembly for Linux finishes the book. The Windows platform is not that much covered but there are plenty of links distributed throughout the net to make up for that. After reading this book it is relatively easy to get a grasp on all those pages on the net that assume that you have prior knowledge about Assembly. Now, I can say that at least I know something about Assembly with a clear path ahead; With Duntemann's book on my shelf, I have a good reference for all those little "MOV's" and "EDI's". I recommend the book to anyone interested in learning Assembly from the beginning.