I'm surprised how much I'm enjoying the game. It isn't the deepest of games, but there is strategy involved once you get into the second and third tier of battles (much like a typical story mode fighting game would be, right?). It is fun leveling up the cards / characters and doing the Mass Effect-style "open the prize box you earned with credits and get a new dude" thing is pretty cool.
If anything, this is worth to play for ten minutes to unlock some skins or whatever on the console version. If you want to invest more time and get into it deeper you can do so without paying a cent and have a pretty good time.