Well, it's a little after New Year's, but we're still in wow gold January, so I think that's close enough. Wrath of the Lich King is definitely worth coming back for, even if you don't have a level 68+ to experience the Northrend content. But if you do, it's doubly so. The Achievements are a blast and make leveling up to the new content more fun. Also, leveling is speedier and there are even new quests in the old world to make it seem like less of a grind. It's apropos that so many people are coming back from the "dead" now that we have Death Knights -- you may be just as disoriented as the newly revived minions of the Lich King. Here are some tips for getting the most out of your return to Azeroth:
If you were in a guild before you left, try to return to it (if it still exists) when you get back -- even if it was a raiding guild. I am in a guild that raids every night, even though I don't (it helps that I'm married to the guild leader) and we've had a lot of returning players. Many raiding guilds will let you return to the wow gold guild even if you are casual now, just to have familiar friends back in the fold. Regardless of the kind of guild, you should try to get in with people who have been playing while you're gone. You're going to have questions that they can easily answer.
Guilds transfer, friends re-roll and queues lengthen -- whatever the reason, your old realm may no longer be the best fit for you. The best thing to do is find a server with friends with similar schedules and transfer your characters there or re-roll. Or you could find fellow WoW players from another community in which you participate. For example, Ravelry (a wonderful online knit and crochet community) has both Alliance and Horde guilds as well as a list of all the wow gold realms fellow knitters play on (you have to belong to Ravelry in order to see that link). If you must go it alone, I recommend a medium population PvE server (check at peak times for queues). PvP can really take up a lot of your play time while you are trying to quest (though that's where I play). You don't want too low of a population because that affects the economy. Even if you won't be raiding, you want to be able to sell your wares to those wealthy hardcore types.