Not only is it my favorite, I've found it to be the most survivable. The base set of abilities has been sufficient for me. Kind of a slow and steady wins the race type pet.
Start with Moonfire, then fire up Tranquility, then 2 rounds of breath, repeat tranquility and 2 breath until Moonlight runs out, or use moonfire if facing a flying critter, you need to reestablish moonlight, or you need something a little heavier than your breath weapon.
I've leveled the other dragonkin up to at least 10. I liked the Emerald better than the Celestial and Crimson single heal every few rounds, and while the Azure whelp has a big hitter, the 2 rounds of recovery afterwards makes it questionable. The Dark has the 2 round ability, but I found it missed way too much to be effective.