I've seen this in the store once or twice and never quite felt the need to get it. There's elements of the thing I'd be interested in someday, but I can't quite justify the full price of the book just on the off chance that I'd run it one day, given I don't think such a game would be a high priority and I've other RPG books that I'm more interested in. However, I do keep half an eye on Humble Bundle, and they've currently got a bundle of Doctor Who RPG stuff up. I might not be prepared to pay full whack, but 77p right now for the core book and the first Doctor source book? I can justify that on the off chance I ever read it.
I don't think I'd run a game from a PDF, but having it makes me a lot more likely to one day buy the book from Spirit Games, so I figure it's worth a look, right?
If anyone
else is tempted,
here's the link to the pdf bundle. The main rulebook is in the base tier, but there's a huge load of source-books should you be interested in higher tiers. (Note - The site lets you choose who the money goes to. Cubicle 7, the guys who made the game, Humble Bundle as a tip and the charity seems to be Children in Need themselves. You can configure who gets what at the bottom, near where you pay).
And if you like it, I believe Spirit Games also has it in stock in the infinitely more practical
dead-tree format. 
