As of today anyone who buys the game is entitled to download the beta version of the Mac SKU. It's still being optimized, although it already allows Mac players to log onto the existing servers and play with fellow PC players. The Mac beta is accessible through the Guild Wars 2 account management website once an owner's game code has been registered.

Guild Wars 2 Mac Client

ArenaNet is partnering with TransGaming whose revolutionary Cider technology dynamically translates between operating environments,” a company statement confirmed.