Well for some reason, I can concentrade better when reading a book then when reading it on screen, and despite downloading the entire AS3 Bible in PDF format, I still bought a copy of the book in the end. I could have printed the whole thing out but I really couldn't be bothered.
From my experience with the book, id say it has been worth it. I don't think it explained classes all that well though, at least I didn't understand them much from what the book gave me, maybe it's just me.