How does it compare to other casual action RPG's like Magicka? (I don't mean casual in the pejorative sense.)
The gameplay is actually pretty good, as long as you like Action RPGs. It doesn't do enough new things to win over non-fans of the genre, however it's solidly designed. The Hero Swap mechanic, for example, allows you to have three Heroes - with independant Health and Power bars and abilities, as well as upgrades - in your Squad, and multiple squads. So, for example, you pack a solid all-rounder, an AoE specalist and maybe something that is strong in 1v1, and you swap between your Heroes as needed as you play through.
The gameplay itself is basically the standard A-RPG formula, though with a dose of DotA thrown in; it's less about just mindless clicking, ala Diablo, and more about ability useage - ala DotA. For example, the spider Hero - who's name I haven't cared to remeber - collects 'souls' as they defeat enemy. For each soul you have, up to six, one of your abilities spits out seeking missles. This is handy when against bosses in 1v1. Another ability spits out a massive numbers of smaller missles, again the number depends on the souls you have, and allows you to handle groups of monsters. Each Hero has unique abilities, and some have entirely unique mechanics, and one of your abilities is a 'squad ability' that can be used regardless of the Hero you currently have selected. Matching up interesting combinations to give you an edge is the name of the game. It adds an interesting strategic layer to game, as not only do you need to carefully equip your Heroes, you also need to carefully select them as well. Unlike Diablo or Torchlight, there is no in-game inventory. Your inventory is a massive hoard of the items you have shared between Heroes. You sell and buy them between levels, and it helps to speed up the game quite a bit. No Town Portals, etc.
The game is built around multiplayer, to the point of it requiring an internet connection. I haven't tried my hand at PvP yet, you have to unlock it, but the co-op stuff is where the fun really is. It's faster than, say, Diablo's multiplayer as you just keep moving, however it's balanced around a more difficult game; it gets harder the more players you have, and it really forces you to work to gether to stay alive. The online stuff, like the party system, is ripped right out of the typical MMO UI handbook, complete with typing /party to talk to your party. It works, though it's combersome and hopefully the Beta fixes up a lot of the quirks.
Your player profile can level from 1 - 100, the same as your Heroes, and each level brings new unlocks. The Hero customisation options open up the more you unlock, as well. You have to get really creative with your Heroes to make them unique. I have have been a little too harsh on these options initially, however I still stand by the fact that it's too restrictive. A random and I jumped into a game together, and we both had the same first Hero selected. Apart from our weapon, our Heroes were basically indentical, despite having spent some time trying to make mine unique.
It's an interesting take on the A-RPG.