I use Faithful with -4 contrast and +4 sharpening. These only effect the image review on the rear LCD, since I shoot RAW almost exclusively and can always change any settings. The reason I have tweak contrast is to more closely emulate what the RAW will look like later on my computer monitor. Yes, unfortunately the histogram is based upon the embedded JPEG within the RAW file, rather than upon the RAW file itself. So, as others have noted, it's influenced by the Picture Style, too. So that's another reason I have contrast dialed down as far as possible. The reason I set sharpening high is to make it easier to check focus accuracy on the tiny screen of the camera.
White balance and tint settings will effect RAW in most any software program, but remain completely changeable after the fact. All the other settings only effect RAW if you process the file through Canon DPP, and even then you can turn any of them off or vary them from the Picture Style. I finally figured this out when I had a problem with a shoot... every image was way too magenta. It was correctible, since they were RAWs, but so far off it was a pain in the arse. At first, I thought my computer monitor needed recalibration... so I did that. Then I noticed it was only happening with one of the two cameras I was using for the shoot. Damn, I thought, something is wrong with it and it's going to need to go in for service. Finally I checked the settings and discovered that somehow the Tint slider had been shifted to the way to magenta setting. Up til then, I didn't realize that all softwares (I was using Lightroom and Photoshop, not DPP) will reflect whatever WB and tint are set in the camera. So this is one thing to watch, even when shooting RAW (though it can be corrected... just not very easily when you have 1200 images to edit, and you can't really apply a global adjustment to them.)
I don't put much trust in reviewing images on the camera's monitor. It's too small, subject to a wide variety of lighting conditions that effect both color and brightness dramatically, and impossible to calibrate. I only use on-camera review to confirm focus accuracy (to an extent... I usually won't delete a photo based upon what I see in the review) and to check composition (where I might delete a "miss" based upon the review). I leave image review off on my cameras most of the time, only occasionally call up the last shot to check it. This conserves battery power, among other things. It's also less distracting. I see a lot of photogs so engrossed in their image review that they miss great photo opps! (I've been guilty of that too, at times.)
