Well, it's free to play and they are very commited to ensuring that the cash shop only contains convenience and cosmetic items (so, no pay to win). As far as commitment goes, the skill tree is super complex and there are no re-specs so you probably want to do some research there, but playing with others is very drop in/out and easy, it scales encounters to the number in your party, lots of random loot, lots of random location, I like it (but I'm playing NWO right now)

do you have to commit, or can you play it casual?

It's amazing. Very complex and unforgiving, though.

Is it good?