I will be waiting until they get the Short Story by Jim put in the PDF. Then I'll Pre-order.
Although I'd rather pick my books up AT Origins; I'm running two slots of a DFRPG con game, and it'd be good to have a copy of the game at the table. If for no other reason than to show the players.
Just to make sure you're aware: You can download it more than once, and you can sign up on their site to get email alerts when they update the pdf -- so you should only wait to preorder if you're trying to space out big expenditures or something.
Since I
didn't get the nifty preview certain Origins-attendees may have gotten, I've already preordered & downloaded and partially devoured the books.
They're... really neat.
Book 1 is a complete game system with all the rules you need to play and the sort of background material that you need to say "White Court Vampire" and have it make sense; it namedrops a LOT of Dresden Files specific content, but strikes a nice balance of being atmospheric while not wasting page count on fanwank. The discussions between the 3 "authors" (Harry, Bob, and Billy) are
awesome, the examples are great, and the powers are pretty well thought out.
Book 2 is pure -- and delicious -- fanwank. If you're getting the game for the system and don't care about the book series upon which it's based, you can skip book 2. You'll miss the bestiary and Chicago, but the bestiary is pretty specific to the books, and honestly you don't need it depending on how much house ruling you were going to do; the design guidelines are all in Book 1.
Full disclosure: I've been running a fantasy hack of Spirit of the Century for a buncha months now in preparation for this to come out, using a 1e DMG and a 3e MM; my plan is to basically swap out my SotC houserules for this book and keep on plugging. I haven't missed having a monster manual yet, and DFRPG looks like it'll be even awesomer.
I bought Book 2 because I like the Dresden Files and wanted the encyclical.