It's a bit rigid and boring in most cases, I'd imagine. They can only have anything in moderation lest they attract the gaze Slaanesh.
As for the five major Craftworlds they're something like this:>Alaitoc
Everyone has an immovable rod up their ass and gtfo when they turn 218. They are not a cheery bunch.>Biel-tan
Militaristic assholes who want to enact genocide upon everyone who isn't an Eldar. They can be cheery, but only if filthy mon'keigh are burning in the background.>Iyanden
No one laughs here. Ever. Half the population is stuck in virtual limbo and the scenery is mostly trashed in some places. They're the toughest crowd a stand-up comedian could have. Cegorach couldn't make them smile.>Saim-hann
A wild bunch. Among the CEldar they're basically the cool kids who ride on motorcycles and won't stop even after they start getting their pension. They laugh when they leave you in the dust or run you over like an animal.>Ulthwé
Constantly under attack by whatever the hell it is the Eye of Terror is regurgitating this week. They are a bit more mystic and spiritual than everybody else and won't shut up about how deep and smart they are. They generally have a pretty good idea of what the future holds, but just enough to know that they're just stalling for time by acting on what they know. The scenery is pretty trashed by Daemons and because of said Daemons trashing the scenery when they show up, everyone is considered to be a soldier, even more so than on other Craftworlds. Because they spent time and effort decorating the place, and they don't take kindly to anybody who shows up to trash the place. You can make these guys laugh, but they have a very dark sense of humor.
Basically, everyone is an arrogant dickhead and you're all going to die. Until then there are no fun times to be had by anyone, only less boring or horrible times.