I wasn't paying much attention when it released, but from what I've seen, it looks like it got pretty miserable reviews. Well, a lot has changed, and I must say that I've spent way too much time playing this game which is a good sign for the game and an awful sign for my social life. I went in with low expectations and was pretty underwhelmed at first, but the game turned into something that I love playing. It's free to play, so I highly recommend checking it out for yourself.
The most annoying thing about the game is the severe lack of stash space. The ONLY way to get more stash tabs is to spend $5 bucks per tab which I feel is more than reasonable. Also, when it comes to unlocking more heroes, there is a currency called Eternity Splinters that you can use to purchase a random hero or purchase the hero you want for a higher amount. The random unlock costs 175, and the heroes themselves range from 200-600. To give you an idea of the rate of acquisition for these items, I've purchased 4 random heroes in two weeks along with a few other things for smaller amounts.
When it comes to gameplay, there are multiple things to do. You can run Cow Level, go through the story on three difficulty settings, do an endless mob wave type event called X-Defense, there's PVP, Legendary quests that take you all over the place, and end-game instances called Terminals. Supposedly there's also a raid type event on the way. Pretty much all of the events can be done in a group and all of them minus the Terminals automatically group you up unless you form a group of your own. Also, you can pretty much do whatever you like at a very early level.
If you do decide to check it out, here are some helpful tips:
1. When you pick a starting character you are locked in until you obtain more characters via the item shop or in-game currency
2. Respecs (Retcons) are pretty rare, so think about where you're spending your points
3. X-Defense is a complete clusterf**k, but it's a good way to get loot and levels
4. Mobs called Doops are loot pinatas so don't ignore them
5. Level up your crafter and enchanter by donating items to them as opposed to vendoring items. You unlock more/important recipes by leveling them
6. Don't pick Black Panther or Black Widow as your starting character. They suck right now, and are in the process of being reworked
If you have any questions/help or would like someone to play with, my name in-game is Draejan.