I'm actually not sure it affects RAWs at all, it might just control the jpeg that cameras insist on making from them.
In any case if you're shooting RAW you probably want it off. Your computer has a lot more processing power at its disposal than your camera, and your raw developer has an interface bigger than the camera LCD. Both of these things let you do much nicer noise reduction yourself when developing raws than your camera could ever do on its own. >>3496207
There is a lot of stuff in exif metadata, including what metering mode was in force when the picture was taken. Your editor should let you see this, though it'll probably be under some "just show me all the metadata" option.