I can't tell you how much I wanted to like this book. I've admired O'Reilly's technical books for years, and now that I've branched out into business applications, I was delighted to see that they had, too.
When I finished business school last year, one of the classes I had to take was in financial modeling, and it had a heavy Excel emphasis. We did a little bit with Macros and VBA, but the most complex model we did was nothing compared to what this book aimed for. Finally, I was going to get a chance to really gun the program up into 6th gear. Clearly, this was a book that wouldn't talk down to me.
First, even finding the spreadsheets online was a little bit of a task. The URL was only mentioned in the preface. A more prominent location would have saved me a lot of time. In fact, the data spreadsheets should be available without the code at all, just the data (in addition to the completed applications). Most people who want to learn are going to try to work through the application from the ground up.
Secondly, having an editor do just that would have helped immensely. I started on the first application (analyzing call center call volume), and couldn't figure out how the predicted values were arrived at. They weren't spreadsheet functions, just numbers next to the raw data. This pretty much stymied me right there, although I did go on to complete the application, skipping that part. Still, in a book as dense as this one is, where every piece represents a potentially useful application, leaving that much work as an exercise to the reader is unnecessary and confusing.
A minor detail: when using a workbook like this, I find it's much harder to do so if a screenshot isn't on the same page as its description. Flipping back and forth, again, in a book where every sentence matters, really slows down the process.