I'd like to echo KEJR's thinking: My players are notoriously reticent to shell out for expensive (above US$25) books, and this leads to them using my books at the table, as well as borrowing them for character advancement, etc. Now that my table is going full-bore PFRPG, I will be insisting that they each purchase a PDF, and for $9.99, i can't imagine any of them balking. This is in addition to the hardcopy I have pre-ordered and the PDF I will be buying for myself for search purposes.
To wit, that's 5 PDFs sold to people that would NEVER have bought a $40+ book, plus a PDF sold to a gamer (me) that was gonna buy the dead-tree product regardless- that's 6 extra copies to 1 gaming group, and I'd bet there will be a lot of that going around.