1) Druid's were buffed as tanks, this makes them better at tanking 5-man instances which is what the game is all about at the moment. Look here to see a warrior say it:
http://forums.wow-europe.com/thread.html?topicId=120473857&sid=1&pageNo=1
That's maybe not all the factual evidence you'll ever need but I'm too lazy to do look up ALL the links supporting this.
2) No-one cares about Onyxia or BWL or even Naxx anymore. End-game TBC is what people want, and we don't know who is going to be the better tank there. Personally I think it will be a warrior with druid and pally off-tanks. The days of warriors monopolizing the tanking role IS over.
3) Cheetah is gained at lvl 30. That means for for 10 levels you can outgun almost all other classes (Except for shamans, they get ghost wolf at lvl 20). You also can't be polymorphed and you can just shapeshift out of snaresand roots. As a mage I find it VERY frustrating when I see a druid and I know it's useless to try sheep him. Oh and it's instant cast so if a nooblet roots you and starts running you pop this baby, break his snare and he's almost certainly n00b-stew.
So in closing I would like to say that I think druid's are awesome. After writing this reply I'm really in the mood to go roll one. Gone are the days were druids are pigeon-holed as healers. They are now truly hybrids. And if you're guild doesn't want to let you do some tanking they are full of ****, go find a new one. There are people who see further than their noses.
I'm off to go roll a druid, cheers.