While the OSX client is still in beta, it is available for anyone who has purchased Guild Wars 2 to use. Players using the client will have access to the same servers and features as those on PC.
This is an interesting move on ArenaNet’s part. To my recollection, the only other MMO to have OSX support so close to launch was World of Warcraft. However several have added support well after launch. The problem I generally see with this is that many people have no desire to join a game that’s already been running for a few years. So, I’ll be interested to see if adding support early on boosts GW2’s numbers further as they hit those people that otherwise wouldn’t be playing MMOs.