After 7 hours of sitting in the Darkmoon Island forest (that's seven attempts total), I'm now a proud owner of Moon Moon! :D
The event comes and goes like clockwork, and it's fairly straight forward except for the fact that you must actively help Moonfang spawn by killing smaller wolves. I didn't have any problems with this, though, minus the elite wolves that spawn as the second "phase". Those need a couple of people if you want to kill it within a reasonable amount of time.
Other than that, you just need to be careful not to kite the wolves or Moonfang away from their original spawn area. They have a high rate of evading and then returning back to their spawn with full health (if you drag them too far). It's especially annoying if Moonfang does this, as that means everyone will need to work on defeating the world boss all over again.
One thing that should be mentioned is that although you can loot this boss multiple times a day on a character, sometimes the body won't have any loot for you at all. There aren't any trash or vendor items to be had; Moonfang's loot table only consists of unique-bound vanity items. The "no loot" scenario is likely due to the fact that 1 - you already have one of the unique items, or 2 - the internal random roll for loot just didn't pick any of the unique items.
It can feel a little disheartening when you run up to loot Moonfang only to find nothing available, but thankfully you can just try again. She's taggable by all too, so it's not like you'll be competing with any specific group or faction for a chance at the pet or other vanity items.
Overall I'm pretty satisfied with how this was all implemented. Limited time (one week out of the month), but a "high" rate of spawn (once an hour) that you can participate in and loot as many times as you want. The droprate isn't too high or too low, which balances out nicely with everything else. Being able to tag the boss for personal loot is also a huge plus that I think everyone appreciates. No chances of "ninja looting" here!
I'm still a little concerned about how this event will play out on low population servers or when the novelty/popularity has died down. The DMF is CRZ'ed, though, so there should generally always be some players there, but what will happen when most don't even want to bother killing Moonfang anymore? Will they have a significantly harder time with the encounter?
Keep in mind that this isn't taking into account that the event probably won't be outdated until maybe next expansion, when the level cap is higher and we all have more gear. If you take that into account, perhaps it won't require a large group of people to take down Moonfang, and smaller groups who are still interested will be able to do it just fine. We'll have to wait and see how it plays out in the long run.
Last but not least, I've updated my Look-a-Like Challenge to include Moon Moon. :) I must say, it took a few attempts to get a good screenshot. Moon Moon kept wandering off just as I was taking one. Damnit, Moon Moon, stay still! :P
Oh, and if you target Moon Moon and emote dance with it, you're in for a cute surprise! :)