Short version: This game takes you back to the good old SSB-brawling-with-your-friends times. The rule changing mechanics are a really nice idea. Recommended specially if you have firends/family to play locally with.
TLDR: Keep in mind that this is an early review. There are many things the devs are working on.
Controls: Controller works GREAT. It feels fluid and intuitive, you won't catch yourself having a hard time switching cards, jumping and hitting someone at the same time. On the other hand, keyboard controls feel plain out weird, specially on the card-controlling part (controlled using u, i, o, j, k, l). My first games were played using this imput method and it could sometimes get frustrating. This point is further aggravated by the fact that there are no remapping options at this point.
Gameplay: This is the strongest point of this game. It is a 2D brawler with constantly changing rules (tag, king of the hill, racing, FFA and more), which are twisted further by players constantly playing their cards to, for example, double the points given or disable melee attacks for some time. 4 player games can get insanely fun, specially (as I already mentioned) in local games.
Community: Right now the community is pretty small, and it can take some time to find a match to play in online. This can get frustrating at times, especially if you experience the "UPNP router bug" which won't let you create a lobby (which the game will automatically will do if it can't find a situable match, forcing you to lose even more time as it can't be cancelled until the error shows up).
Overall: The game is fun, but does not feel complete yet. If the genre draws you in and you don't mind encountering a few bugs along the way, you will surely have a nice time playing. The devs are active in the forums and the community seems to be growing in a by-day basis, so even with its current flaws, I recommend this game.