Having done a lot of PuG raids in the past week with different guilds (yes, they're PuGs... but the majority of the raid tends to be composed of the people from the raid leader's guild), I was inspired to do a companion post to my previous one on raid leaders; this one being on the topic of how raids are run.
My Guild: Raids are casual. Teamspeak and raid chat often have people goofing around, although we do limit off-topic conversations to guild chat and shut up when our raid leader is giving instructions.
Kael PuG: Very casual. The raid leader gave no instructions except to ask if I had seen the fight (I had) and to Misdirect Capernian to a warlock. However, there were no "noobs", so we all figured out what to do quickly enough to one-shot Kael.
Vashj PuG: Casual; similar to my guild raids. The raid leader gave clear instructions, asking specific people for their cooperation but being fairly general. He also made that particular fight as easy as possible for the less experienced players by taking it on himself to stand at the top of the stairs each time to catch the cores, and only passed them to the more reliable players.
Illidan PuG: All business. No-one mucked around, and no-one talked in Ventrilo except the raid leader, who gave very detailed and specific instructions. In one silly wipe where a (usually reliable) warlock pulled aggro within seconds at the start, only 2 emotes were directed at him to acknowledge his mistake, and all the raid leader said was "Phase 1 is not a DPS race" (not in a mean way; more like a parent telling a child something important).
It's definitely refreshing to join a raid where raiders and/or the raid leader treats it very seriously. It's efficient, for one thing, and you also don't feel like anyone (or anything) isn't pulling their weight because everyone does what they're supposed to do.
However, I don't think I'd be able to do that all the time. I'm rather sociable myself and don't mind wiping a few times if we're laughing while we do it. I know I'd probably progress more quickly through content if I joined a more "hardcore" guild, but.... I think I'd prefer the social aspect in the long run.
Besides... there's always PuGs.