Okay, time for a minor pet-peeve. If you're going to include a DVD with a book that includes sample implementations of concepts you MUST make it a requirement that people include some kind of sample for EVERY CHAPTER. I realize that's an additional burden on the author, and the editor might go through hell trying to wrangle all those chapters. Oh, and no doubt there are concerns about code quality, and lots of experimental code tends to be a little spaghetti-ish. But frankly I'll take anything if it can show me a sample implementation I can just quickly rip apart and get to the meat of.
Implementation details are often left out, or left unclear, or just left as exercises for the reader to discover. Given the purpose of a "Gems"-style book - which is to provide a reader with insight into *implementation* details and not simply to get some idea published - it's important that the reader can walk away with as clear an understanding as possible.