Originating as a flash game and making it's way to the PS3's downloadable game store, flOw is often described as an experience rather than a game. This is why I feel that you should not play it and nor should anyone who cares about gaming.
The gameplay if you can call it that is simple enough that you'll eventually question why you're even bothering with it. You gain control of several creatures during the course of the game, and you guide them around the screen by tilting the PS3 controller in the direction you want to move. This feels like a cheap attempt to steal some thunder from the Wii and is much less efficient and enjoyable than using the analog sticks would be. It's also required.
The idea is to eat the creatures smaller than you in order to grow, and to also tackle the larger creatures by eating away at their glowing spots until they fall apart into a bunch of smaller critters.
There's very little opposition. You eat as much or as little as you want on a particular screen, then find one of the tiny red critters hiding on the screen. Eating it will allow you access to another screen at a lower depth where there may or may not be more challenging creatures to eat. It seems that if you get bitten enough times, you get sent back to the previous screen, but you can just eat another red creature to go back and try again. You don't even have to worry about getting large enough. You can pick away at something, get sent back, then return to continue picking away at it. But since seeing your creature evolve is about the only thing that comes close to being fun, you might as well work at it a little bit. You can't get a Game Over no matter what you do.
Getting far enough will allow you to change creatures. Almost all of them are wormlike with minor differences, and each has a unique, though mostly useless ability. One creature can paralyze other creatures, one can do a spin attack, etc. You can make use of these, but rarely are they necessary or fun to use. Fortunately, as you reach the end of the game, you'll face a tremendous and amazing boss that... actually, I'm lying, all you get to do is control yet another creature to eat the end credits. But that's better than a cool boss... right?!
Perhaps I'm lacking imagination, but I can not immerse myself in this "experience" the way some people seem to be able to. Are the visuals and sounds pleasant for a while? Sure. But it's a very short while, and then you get used to it like you do everything else, and you have an $8.00 experience that provides about the same level of entertainment as a free web game you might play on your lunch break. I strongly advise staying away from flOw unless we want to give the impression that we want more experiences like this. I'd personally prefer actual games, and I hope most people would.