tl;dr if you're thinking of buying a digital copy of Diablo 3, you're now essentially paying for a timed demo for 72 hours before you can progress past Act 1.
As of patch 1.0.3, when purchasing a digital version of Diablo III through the online store or your Battle.net Account, players are restricted to the Starter Edition for the first 72 hours (sometimes less). Players on Starter Editions have the following restrictions:
Act I up to the Skeleton King is available
Level 13 cap
Matchmaking available only with other Starter Edition players
No Auction House access (Real Money or Gold)
Global Play is not available. Players attempting to connect to Diablo III Starter Edition in a region other than their Battle.net Account's home region will receive Error 12. See the Global Play support article for more information.
More information regarding the Starter Edition is available here:
http://us.battle.net/support/en/article ... guest-pass
If you are still encountering the Starter Edition restrictions over 72 hours past the date of purchase, please let Customer Service know: http://us.battle.net/support/en/article/contact