Leves are an excellent idea, much like a lot of stuff in Final Fantasy XIV. The idea of being able to grab different kinds of work at an easy to find central location and get stuff done in a relatively short amount of time? Sign me up. As a few others have said, they tie into the story of the game(or at least give the impression that they will), and they make you feel like a mercenary taking work for different people.

The problem, much like other systems in Final Fantasy XIV, is in how they were realized. There's hardly any variety other than "go kill x number of mobs", "go kill x number of mobs to farm y item", or "go kill x number of mobs at y locations to spawn z big mob". These are admittedly staples of MMOs in general, however they're hardly enough for the kind of gameplay experiences we're used to in games nowadays.

What we need are different types of objectives. Let me escort cargo/people through beast(or beastmen)-infested territory, let me defend an aetheryte camp, let me aid some gladiator in his daily training regimen, or explore some areas for a survey expedition, etc. The system for all of this is already in place, now let's kick it up a notch. With the way they introduced sidequests, they have the ability to incorporate non-repeatable story chains in addition to the small quests they've added here and there.

Yoshi and his crew have pointed out several times that they plan on adding more quests and leves through every update, and I hope(and like to think) that he and his team understand that it isn't just about quantity as much as it's also about quality and variety. I really think that leves can be something pretty special if they can pull that off.