I was very late to this game (only started playing during the most recent expansion), but I love it to bits. I've played MMOs in the past (XI and WoW) but this one really sucked me in. Its story (especially Heavensward) is one of my favorite in Final Fantasy period and the references and fan service to the series are excellent.
If you remember the bad press from its launch you might be interested in these documentaries covering how the game was rebourn into what it is today. Both are great;