This easy to read book is what finally got me to start with Ruby (and Rails) development. Most of the arguments are sound, and the history of C/C++->Java->Ruby(& Python, etc) was fascinating.
However, as a long time Java programmer I read the book with mixed feelings. Much of the 'pain' we Java programmers were supposed to be feeling had already been alleviated by the incredible 'eclipse IDE'. Bruce Tate has many valid criticisms of Java, and certainly when you compare the metaprogramming capabilities of Ruby to Java, it does look quite archaic. The question of static versus dynamic types is much less certain, as the wonderful command-completion and refactoring capabilities of eclipse seem to be largely as a result of Java's static typing. As a result I felt that while the book was making completely valid points, they were perhaps exaggerated a little more than necessary.
Now two months later, and a few rails applications under my belt, I should say that the dynamism of ruby (and some other niceties like duck-typing and method blocks) has won a convert in me. And of course the conveniences of the Rails platform are undisputed. And most recently with the advent of JRuby 1.0, I think we will start so see a much faster adoption of Ruby by the Java community. JPython went far, but not far enough. Bruce seems to think Ruby will fare a lot better, and I agree with him. The next few years are going to be very interesting indeed.