This game is not your casual Pokemon rip-off. Worth playing and really satisfying in most of aspects.
But... I was wrong.
The first thing which makes this game original, is the Invizimal-searching part. You scan the environment around you with the PSP camera searching for these beings. The annoying part is Invizimals hide in variably coloured things. Sometimes it can be problematic searching for the right hue, but for me it is OK.
When you lock an Invizimal, you must complete a challenge to catch it, like jumping hill to hill with the Hilltopper, evading clouds with Skytalon or tapping the beat for Beatwidow.
Fights are packed with a bit of strategy. You must know what attacks are good against each types of Invizimals. Attacks also drain Stamina. The more powerful the attack, the more Stamina it drains, so be warned. Defending against attacks also drains Stamina. If you're out of Stamina, you can't do anything, so you must watch the Stamina bar carefully. There are special "Vectors", which can help you in battle, like Life Pack or Earthquake. And there's online mode too, where you can fight against other players and win Invizimals or Sparks, the currency in the game. Invizimals can also level-up. Usually, an Invizimal is a Pup when caught. Then, it turns into a teen-ish, bigger monster. The last form is the Adult form. When Invizimals level-up, you can boost their 5 stats: Life, Stamina, Stamina Recover, Armour, Attack. All of them are useful in battle.
The plot is somehow good, and it fits with the theme of Invizimals.
Collecting all of the Invizimals can take some time, so it will entertain you for a long period. For me, it doesn't deserve a 7.0. It is better than that.