Guilding doesn't do all the much. You get a special cape, and a guild hall(if teh guild master can afford it). But neither of them do anything aside from having aesthetic qualities. The guild hall is basically supposed to be a meeting ground for planning things and whatnot, but obviously all Guilds use TS or Vent anyway, so it's pointless since you can't actually DO anything in your little hideout.
The only benefit of joining a Guild is more coordinated teamwork, and usually fellow Guild members will give you good deals or help you get cool items. Nothing that you couldn't do by finding some non-guild friends or random people to go on a quest with. Unless you're a huge fan of guild on guild arranged battles, there's not much joining a guild can do for you.