For me, this is a great game on the PS Vita. The game is never boring as there is always that element of 'should I use the power up move now, or build it to level 2 or 3' and you never know how good a player will be online! Also, every character has their own, individual moves, which you can learn - but I haven't yet as I think there is too much to remember. However, this is nice as it adds to the overall 'build quality' of the game, and that no two characters are alike.
There isn't a strong story line, instead each character you choose, you view a 2 minute video (which is good if you may not know the story behind a character) and you complete a few fights with other characters and then fight the big boss. I found this to be good fun, as if you don't know the character well there is an introduction. However, to my disappointment, you can't save in between when you are playing a character's storyline, so it can be very frustrating if you don't have enough time to finish it, and have to restart the whole story again.
Online is fine, I did have a few connection problems but in general it did work fine. To find a match, it is very simple, you just need to choose you character and it'll fine games. This may be a negative for some, as they may want to customise their games with other people.
Other than that, it's a great game that I really enjoyed. The graphics are great too however I hope there may be characters added in the future! Every character is different and have their own individual special moves (however maybe there should be a small notification that reminds you of the characters moves - as to be honest, I forget most of them!).
A great game, especially for the price.