The magic date is 15 May 2012 and the digital version is available for pre-purchase right now for SGD90 (USD71.57) through Battle.net.
On pricing, I’m a bit unsure which option to go for seeing if you’re in the US, the digital version will only set you back for USD59.99. On the other hand, Amazon will sell me the physical standard edition plus shipping for USD75.97. Clearly, I’m not gonna get the Collector’s Edition, chances are I probably wouldn’t bother with most of the freebies along with the fact that they’re all pretty much sold out everywhere.
Also, if you’re a WoW player, you can get the Diablo III for free with the purchase of the WoW Annual Pass. Not only will you be getting the game free, you’ll also be getting Tyrael’s Charger (an exclusive in-game mount) and guaranteed beta entry into the next WoW expansion! Sounds like a great deal to me if you are still in WoW.
Addendum: I hate that it’s online only, what happens when you’re fighting a boss and he’s down to 1HP and your internet connection falters?