I'm enjoying the game (as I did the beta)... the only thing I can say that concerns me, in regards to looking at the future, is that 95% of the pop-up events aren't going to be doable when the lower level populations taper out a couple years down the road. There won't be enough of a horde of players to take out... say that troll in Queensdale for example. And since the game scales you down to the level of the area you're in, you won't be able to come back and do it for fun at a higher level.
Granted, this isn't a problem they're going to have to deal with for quite a while, but at some point, it will become one.