I have always been a fan of game demos, the reason why is simple. It allows you to check out a game without really buying it, or today downloading a copy.
The following is a list of PSP Game Demos that I originally downloaded from PSN and what I think of each game. Mine you these opinions are solely based upon the demo and not the full finished version of the game...which will be reviewed later if they already hadn't been.
Buzz
Quiz game and I thought it was quite fun
Echochrome
A really weird type of puzzle game, made no sense to me
Hoard
Yet another strategy game, except you main character is a fire breathing dragon. Interesting yet fun.
Loco Roco Midnight Carnival
One of those types of games you got to get a character from start to finish. Really fun, and quite unique
Motor Storm Arctic Edge
An absolutely incredible racing game, great vehicles, incredible tracks.
Patapon
One of those games you have to listen to clue so you can tap out a beat for the characters to follow. Not one of my favorite types of games.
Pixel Junk Monsters Deluxe
A unique mixture of both action and strategy, I find the gameplay interesting. I have to see what the full version is like before I give final judgement on this game.
Undead Knights
Surprising good game, lots of blood, and good controls. I found it got a bit repetitive having to kill the same enemies over and over as they respawned.
Worms Battle Island
This one I really didn't like, combine moving your characters, while getting bombed. Not fun