Well is it only using 50% of PS3s power?

who said that

Apparently, Kojima used 100% of the PS3's capabilities: http://www.psxextreme.com/ps3-news/3076.html

And later, he [Kojima] said he was disappointed with what the PS3 could only offer: http://forums.maxconsole.net/showthread.php?t=108799

Here's his answer from that last link:

"Game-wise, it's pretty close to the original vision: you sneak into the battlefield and can choose whether to do a stealth game or interfere with the battle more directly. But the graphic, side things like motion-blending and the size of the map, totally was not accomplished to my original vision - to my satisfaction.

When we first showed the game engine at TGS, the staff were really proud and happy. PS3 was a dream machine, y'know, and we were going to work on this and that - and we had so many ideas. But when we actually started developing the game, we realized there were a lot of restrictions and so it turned out how you see it today. The original vision was to go ten steps further, the reality was just one step, which isn't to say we didn't progress.

I remember saying three years ago that we wanted to create something revolutionary, but in reality we couldn't really do that because of the CPU. We're using the Cell engine to its limit., actually. Please don't get me wrong, I'm not criticizing the PS3 machine, it's just that we weren't really aware of what the full-spec PS3 offered - we were creating something we couldn't entirely see.''

 I think I read it somewhere.

This is correct.  The developer said that the beta version used 89.7316572% of the PS3's potential, but that it would have completely destroyed the market for other games, so they dumbed down the final product so that it only used 50%.

I think I read that in Game Infarcer or some other magazine.

Kojima has alerady said he was miss quoted

Not even close. Most of the power goes into heat, but the newer interiors creates less heat, so it uses a bigger percentage of the newer models power than the older model. Also there's a difference are we talking about BC model or non-BC model, since the BC model has GS inside, which isn't used in MGS 4, so that makes the percentage even lower.

I hope i cleared the thing out.

Any time someone says "It uses x% of the consoles power!" they are wrong and they are very very silly for saying such things.

Consoles and PCs simply do not work in terms of usage percentages, there are far too many parts of any system that can be the bottleneck in any number of scenarios within an application for any number like this to be anything but pulled out of someone's ass.

Its a nice soundbyte for consumption of those who don't know better and are willing to gobble it up.  Outside of that its useless...utterly.

Or you think he said that. Link or it didn't happen! D: