Guild Wars 2 Servers and Regions Details

The folks at ArenaNet have put online an article which offers more details on the different regions' versions of Guild Wars 2 and the various server and language options. Here's a snippet on homeworlds and server transfers:
The very first time you start the game, you'll be asked to select your home world.

By default, we display the worlds that are hosted in your regional data center, but you will be able to select a home world from either region at this time. So, for example, if you are a European player who prefers to play on the North American worlds, you're free to do so.

At launch, players will be able to transfer between worlds freely. However, once server populations have largely settled and stabilized, world transfers will be restricted to once a week and cost a variable amount of gems based on the population of the world being transferred to.

In time, we'll also introduce free (guesting,) which will allow players to visit other worlds as guests as long as they have friends on those worlds. This feature will be free, but guest players will not be able to enter World vs. World, and the Power of the Mists bonuses from their home world will continue to apply to their characters.