Veteran players still get something extra out of the weekend, with double XP activated the whole time so that everyone can advance that much faster. So whether you've never played the game before or just haven't leveled a particular set of classes yet, you can get a boost through Sunday. You'll also get an exclusive in-game badge for participation. The game's open beta is scheduled to begin this winter, so this will be the first chance in a while for players to get in and see whether they like the game.
[Source: Square-Enix press release]