I'd imagine we'd get the game around 7 a.m. To be honest I'm annoyed with the pre-load, though. Valve have made it completely pointless. At the moment Steam is telling me, "When the game is officially released, you'll be able to play it immediately." Obviously not, because at the moment my L4D folder is 1.5 GB or something, and the game requires 7.5 GB...Meh, never mind.
Uh I hate to wait till Friday, I would have got it off STEAM but I simply couldn't justify paying the extra ?13, it's 22 (inc P&P) from Amazon, from STEAM it's ?35 which is just crazy.