The NDA on the Marvel Heroes closed beta has lifted, and having been there since the start, that's personally very exciting for me. For weeks I've been wanting to talk about the game, but unfortunately could not.
It's a pretty intriguing game, and one worth discussing, not only because its Marvel's first MMO, but also because among the thousands of MMOs out there, it's surprisingly unique.
First off, let's cover what Marvel Heroes is not. It's certainly not a DC Universe Online clone as many were accusing it of being when it first went into development. I'm a fairly big fan of DC's MMO, so this isn't a criticism of either game. DC Universe is an incredibly dense and complex MMO with some action elements sprinkled on. Mechanically, a superhero World of Warcraft with a focus on instanced content is not a terrible comparison.
Marvel Heroes on the other hand will much more likely draw comparisons to Diablo. While most traditional MMOs (even DCUO to some extent) feature some variation on the "click and watch" game play approach, Heroes is much more twitch based. Attacks are directional and must be aimed, there's no auto attack option, and you'll be expected to be constantly moving to avoid attacks and grab power-ups.
Marvel Heroes is also not a persistent world, like many MMOs strive to be. Almost every area is heavily instanced, and even the "public" hubs won't feature more than a couple dozen players at a time. This is for the best though, as Marvel Heroes is also not a very customizable game.
Unlike DCUO, wherein collecting outfit and clothing options is a major part of the game's loot system, you have very little control over your look in Marvel Heroes. This is due to the fact that unlike other MMOs, in Heroes you are playing a pre-existing character. You'll play as Spider-Man, or Deadpool, or Wolverine, or Rocket Raccoon, and each of those characters look a certain way. There are optional "premium" costumes for these characters, but that's really as far as your aesthetic customization is going to go. Because of this, the fact that you're dropped into areas with only a handful of other people is generally helpful to avoid situations where fourteen Hulks are running around.
When I say that your Marvel Heroes character isn't customizable, I'm speaking on purely visual terms. In fact, character development in Marvel Heroes is probably the biggest facet of the game. If you enjoyed comparing loot in Borderlands, you're going to love Heroes. Loot drops constantly (and I do mean constantly), and your character has half a dozen or so slots to fill with weapons, armor, and other power-ups. You'll spend a healthy chunk of the game considering whether a little extra attack is worth a little less health regeneration, and similar scenarios. This won't appeal to a pretty healthy segment of the MMO playing population, but for anyone who lost hundreds of hours in Diablo, it really works.
Overall, I would avoid even calling Marvel Heroes an MMO whenever possible. It's certainly an online game, but you're much more likely to experience most of it solo or with a group of friends. And while it's definitely an RPG, it generally borrows from that genre rather than revels in it, and the action elements of the game play a pretty huge role.
All-in-all, Marvel Heroes is not a substitute for those looking for their next World of Warcraft. But if you've ever been playing Diablo and thought, I really wish I had a jet pack and laser cannon right now, this might be the game for you. Plus, it has Rocket Raccoon, and there's not a lot that can top that.