It makes you very aware of the lighting and the terrain you're hiding in.

MGS3 had a similar system, except you had to manually select your camo (Green and browns when you were in the grass, switch to grey and blues while you're in a stream, etc.)

MGS4 has a neat thing that doesn't make you invisible, but greatly encourages stealthy, methodical play.


Although you CAN just blast your way through some areas, as I learned to my chagrin as I watched my new-to-MGS friend play it.

I'd suggest putting the difficulty on Hard, and go to it.