For the record, I'd never buy ONLY the PDF copy. I way prefer to read the bound copy. It's more comfortable, and way easier to read too.

I have 2 of J-Walk's books, though, which come with the PDF on CD. The CD's are at work so that I can quickly look something up that I've read about at home but can't quite remember.

A complement, certainly not a replacement.

Just got this book (Professional Excel Development) in the mail 2 days ago as well. I'm up to chapter 3, and it seems awesome so far!