Not as good as I expected it would be and if you don't have Diamond/Pearl, This game is pointless.
You should not buy this game if you don't have Diamond or Pearl because Then you would only have 2 of the weakest pokemon parties imaginable and you would have to do every battle with them (even online!)
Anyway, Here's the summing up:
Graphics: WOW! just... wow. 10/10
Gameplay: Like other pokemon games, This one is all about doing turn-based battles using your caught pokemon. Just that, on this one it has several twists like CC (completley customiseable) trainers from how they look like to what quotes they say, The different battle stages have different rules, online battles and much more. The only problem is that like most of the game, It's lacking depth. 8/10
Story: The only bit of story in this game is at the start. You're a trainer from a land far, far away and you've taken you're time to visit Poketopia (basically a pokemon version of Las Vegas). But wait there's more, Master trainers from all over the world battle it out here and you choose your pokemon team and decide to join them. That's basically all there is to it. 7/10
Sound: Like graphics, The sound is completley amazing. 9/10
Music: Same as sound. 9/10
Overall: Apart from lacking in depth in most areas (including online. But I'm just glad there is online). This game is recommendended to anyone who has pokemon Diamond or Pearl! 7.5/10