If you haven't yet decided if Diablo 3 is to your taste, now's your chance to give it a try with what is effectively a demo. Anyone with a Battle.net account can now download and play through the entire first Act of the game and, if its talons tickle your fancy, you can purchase a full version of the game, keep your character and carry on adventuring.
Creating a Battle.net account is free and will only take you a few moments and you can sign up for the Diablo 3 Starter Edition through the "Your Game Accounts" part of your profile.
There is just a smidgen of small print to read through in the FAQ: There's no access to the Auction House and matchmaking is restricted to other Starter Edition players, so you won't be able to play with friends who have the full version of the game. Blizzard also add that if you do decide to pay for the full game, your Starter Edition will remain locked until payment is processed, which can occasionally take up to three days. Three days! Ouch.