Have you really dug into the content yet, though? I know a couple members of my guild decided they would rather spend the day farming Adamantite and Mana Thistle in the 'old' Burning Crusade content because it was mostly abandoned. While it isn't fresh and exciting, it is certainly making them quite a bit of cash.
Me, personally? I jumped in feet first. As soon as the servers came up I was flying to Quel'Danas and putting together a Magisters' Terrace group. My original intent was to get the new daily quests out of the way first, before everyone got home from school or work or whatever it is they do, but the server wasn't agreeing with me on that. Amusingly, after the mobs on my server were killed, they weren't respawning whatsoever. The server actually stayed up that way for about two hours, devoid of mobs, with hundreds of people standing around on Quel'Danas trying to figure out what was going on.