Know that if you tame these you may log on one day to find some normal modeled crocs in your stable. Tame these because they are different skins but be prepared to lose them at any time depending on what Blizz does.
Here are some pics of what they look like with and without BW. The hydras make noises, the heads fight eachother, and they stomp around. As you can see from the pics (click for larger image), the hydras are pretty see through. The slimes are pretty quiet.
In other news, we have both hit lvl 80. I became exalted with Cenarion Circle last night, Consortium is up next today. I still need about 40 warbeads or insignias. Grumble, Tagreth and I have trioed the mount mobs in ZG. They didn't drop for us yet but at least we know it can be done. Also, if you are interested in the ZG Troll faction, it is really easy to solo the junk mobs at lvl 80 if you have a gorilla.