LocoRoco is one of the most unique platformers in years: you tilt the screen to move your 'LocoRoco' from start to finish in a variety of awesome worlds. Thankfully, it works, and it results as one of the funnest portable games that I've ever played.
The graphics in LocoRoco are good, but nothing compared to what we've seen this generation; even on the PSP. That being said, the gameplay and the level of fun in this game is remarkable. Everything you do in this game, whether it be finding collectible items, beating enemies (harmless, kid-appropriate enemies, mind you), or just simply immersing yourself in the playforming experience, I can guarantee you that you will have fun.
Unfortunately, the fun ends soon, as the core gameplay is only a few hours long. Many will find time and have fun playing it again, but I just couldn't really get into it a second time. Different people will be different however, as I have heard of people who have played this for 30+ hours. If you're into beating times and scores and whatnot as well, you'll be pleased, and can definitely add on to the value of this game.
Overall, LocoRoco for the PSP isn't a must-purchase, but I'd definitely recommend it. It's one of the funnest games I've played this year, however, so definitely try and get your hands on it.