More details:
Open Beta starts 5pm (UK time) on April 30th and is open to everyone (though there may be a few queues!). You can download the client in advance from April 20th (which would take a good few hours on the day).
http://nw.perfectworld.com/news/?p=867801 There will be no character deletes between Open Beta and Release - April 25th is the date of the last delete.
To form a guild, you basically have to take a full party of unguilded peeps to the guild master and he'll turn you into a guild.
There will be 5 classes on launch:
1) Guardian Fighter. Like a DDO sword+board fighter, but does decent damage. Fun to play if you like leaping into the middle of things waving your sword around. Your standard left-click attack for instance is just like DDO's Cleave. But you're also expected to act as a tank in parties. They get Dungeoneering skill (essentially like Search and Spot in DDO, but always-on, plus they can operate rare special levers).
2) Great Weapon Fighter. Like a DDO barbarian: two-handed great-swords basically. Like DDO, they are not as tough as a Guardian Fighter. I didn't experiment too much but I would assume it does more damage than a Guardian Fighter. Also gets Dungeoneering.
3) Trickster Rogue. My favourite. Lots of imaginative attacks, but you'll have to dance around your target a lot to get the backstabbing bonus and to avoid getting squished. If you're prepared to keep hopping around this is great fun. Gets trapping skills (which basically means they can spot traps and deactivate them). They get no other rogue-like skills, such as picking locks. Traps aren't common and don't do much damage, so trapping is a minor part of this build. They get a form of stealth, but it's more of a combat ability - they can't sneak.
4) Devoted Cleric. Nothing like DDO clerics. You don't have spell points, and only have a handful of spells available to you at any one time. Everything runs on cooldowns, and your spells don't heal N hp instantly, they are more of the Regeneration variety, healing N hp over P seconds. Other spells include one you can place on an enemy, and every friendly that does damage to that target gets healed an amount proportional to the damage they do. Played a few levels of this and they were okay solo but not great. I imagine they are more group-orientated.
5) Control Wizard. Don't do amazing damage and are really quite squishy. Their spells appear to be geared towards slowing and pausing enemies, and basically helping out group members. I suspect this class doesn't settle down until (say) level 20. If you prefer to lurk at the back and not be responsible for keeping people alive, this is your class!