HGiles: I don't watch R-rated movies, and I don't play M-rated games.
Gazoinks: Any particular reason? I mean, it's understandable if you're under 17 (that's the cut-off, right?). But if you're older than that it seems kind of odd? (Especially for movies. What constitutes an R rating is incredibly arbitrary. See also: The ridiculous reason that Oblivion is M-rated.)
No, I'm definitely over the cutoff. :)
It's a moral decision for me - there's a point at which details stop being useful and good for immersion and start being disgusting. There's a different point for everyone, but the M rating is a good way to say "This game will probably be disgusting to me" vs "This game is probably OK".
There's a difference between having a serious conversation between adults, and having a graphic conversation. For me that's T vs M, subject-matter wise. You can have all the kinds of things in T rated games that you can in M, but how much / how detailed is the difference between the ratings.
And yeah, there are the weird outliers, like Oblivion where the rating got turned into a political exercise. But nothing in life is 100%. If I really think a game doesn't deserve an M-rating I may take a second look at it, but it's not like I'm suffering from a lack of good games to play. :)