The good, the bad, and the thinly-veiled anti-heroes.
This game has a great story, as you will soon find out when you're not scrolling down the dialogue just to get the grindy-goodness of exp. Each quest you partake in will give you a paragraph or two (sometimes more) of nice dialogue that can be witty and interesting, as long as some very nice plot twists. The missions themselves are grindy, as there are about 5 types:
-Kidnap (rescue for Heroes)
-Kill
-Steal
-Rob bank
-Mayhem (destroy things)
Although it's grindy, the combat is very entertaining.
There's many different "costumes", but each is customizable. So you can use lots of different costume pieces to mix & match. The possibilities are endless... well, almost.
Then there's the classes. Look on the official site for more info on these. Even after you max out your character to level 50--which I did around 4 or 5 times--you get access to the "epic archetypes", which will add another 100 hours to your play time. I haven't tried them out myself, as I unsubscribed right around the time they came out. Seeing as how the developers got bought out by NCsoft and have been giving more time to quality content, I imagine that they will be well worth your $15 a month.
Like my title says (The good, the bad, and the thinly-veiled anti-heroes.), you will be somewhat disappointed if you go in thinking you're a classic villain. You're more of a henchmen to a villain who always does what he's told, and despite all the rich content the devs have been pumping out, they always give you the same old "heroes and villains have to work together to relinquish this threat!", so the whole lesser evil thing is dry and boring.
Oh yes, I put the difficulty as hard for one reason: it is. I'm not complaining, though, as it's a good kind of hard: you need to manage your hp, your endurance (what you need to use abilities), your damage per second, and everything else. It may seem complicated when you first start, but once you get the hang of it, you will be working those spreadsheets like you're writing a novel.
All in all, a good (great?) game. I'd recommend this to anyone.