I've played my fair share of MMOs that feel like I've nothing to aim for after a month, but I've played this nearly every day since release and only just getting started with end game.
I've thoroughly enjoyed it, the 1-50 story quest was great for an MMO and it's the first time I actually wanted to find out what happens, it doesn't feel like filler as with most others. It's much more challenging in dungeons/bosses than most mainstream MMOs, there's rarely any boss that you can just tank and spank, you need to know what you're doing. This can be rage inducing, and attracts elitist tools, but in the end feels much more rewarding than having your hand held because it actually takes learning and teamwork rather than just lots of time.
I've enjoyed trying the different classes, levelled 3 to 50 before deciding what I'd enjoy playing in the long end game (highest level gear can take months to complete) and levelled a gatherer to 50 to supply my other classes with precious gil.
I'm not saying this the second coming for MMOs, it has no PvP yet (due to have arenas patched in) so if you're a PvP junkie this will never be for you. Leveling alts is a grind, and you'll be running some end-game dungeons until your eyes bleed. Overall you need to have a soft spot for FF and just see if the game appeals to you or not.