What makes you stick with an MMO during beta?

I've been checking out some early-stage MMORPG projects recently, and it's interesting seeing how different games approach the basics of exploration, combat, progression, and world-building.

One I've been following is RPGFX, which is currently in beta. It's still pretty rough in some areas, but it already has exploration, NPCs, mobs, combat, equipment, and abilities in place.

I'm curious what other MMORPG players think makes an early-stage MMO worth sticking with.