After playing my Hunter to seventy, I decided my next class would have to be a healer or a tank. I already had a DPS, after all. So, it fell on my Druid, since she can do both of those. Hell, she can DPS too.
What attracts me to Druids, are the sheer versatility of the class. We can solo almost as hard elites as Hunters with a little bit of shapeshift, self heal, DPS, sheer damage mitigation and so on, and also be fast killers and survivalists. Stealth is always made of win and awesome, and the ability to do all three things with one class is always fun.
I could heal fine in pre-70 instances as Feral, if I had the gear for it. I could tank and DPS just fine as well, with a quick gearshift. (Note: Itemrack is your best friend when playing a Druid). In PvP I can have some hilarious moments when I get out of combat for five seconds and suddenly I'm in Tanking gear making me nigh impossible to kill. Then, five seconds out of combat and I'm in my healing gear, keeping my entire group up with some powerful HoTs, and five seconds after that I'm back in DPS gear, stealthing behind their healer ready to "ravage him from behind".
My DPS isn't as good as a core DPS class. My tanking is good at times, but I'd rather see the Warrior tank on a boss. My healing is situational at best since I have very few Oh Shi-! heals. But I can do all three with some gearchanges.
Not to mention that I am bloody impossible to kill if I decide to stay alive. I mean, shapeshifting out of almost all CC, travelform, catform + sprint, bearform for sheer damage mitigation, and combining all of these... Well, I can run away from any fight if I choose to. If you manage to kill me, it's because I decided to stay and fight in spite of being outnumbered/geared/skilled.
So, for sheer adaptability, there is no class that can match a Druid.
But my Frost Mage, Protadin, Sub Rogue and Aff Warlock are also hilarious classes. The only class I don't really feel like playing anymore would be my level 52 Warrior. It just got too boring. Also, I've never managed to get a Shaman past 20 even. It gets too boring too.
So basically, try all of them. Today, it takes almost no effort to get any class past 30. And by that time, you should have a feel for them all.