Everyone says Hunter's are easy. Easier than other, but there's a certain touch to them to actually be good, and be a great asset to a group. Most groups can still function with a bad hunter, but when a group get's a good hunter, they start to rely too much on that hunter, and once gone, they can fail, quick.
You have to know what pet to use that's going to benefit your group the greatest, and not just some creature you saw and thought 'He'd be cool!', but actually knowing what move's that creature will have. What pet to use that will benefit the tank, or benefit the other members if the tank can't happen to hold aggro, you can use the pet to hold that aggro. If you learn how to control aggro, and have enough space between you and your pet, you can actually control mobs to just rub/walk back and forth and not get a single hit on either of you.
What rotation to use, instead of just spamming Arcane Shot and Aimed Shot.
Hunter is a class, where you have to learn to work by yourself, at least in my realm, all the way up to 55 or 60 (Forgot which level I joined my guild), I was doing it by myself, with the help of my pet. We're a great class to do off on your own, but in melee range, we suck.
I picked Hunter because that's what I had when I played Vanilla WoW, I've always liked the ranged attack, and was always good at it, I go to Warrior or Shaman, and I hate it.
Just remember, pick a class that you enjoy, and not what is going to do the most damage. You're going to be playing that toon A LOT.