I personally think it's Fanboianese. It's the same response you get when you ask someone what's the benefits of rooting, It's just personal preference. I'm sure anyone that would chat up the "pure google experience" would just as well root the phone and those that would tell you how great it is to root the phone would just sit on the same rom for about a year. To me it's not a deal breaker for what I need the phone to do.
One question I wonder, with Google purchasing Motorola Mobile does that mean that their support of the GN will not be as comprehensive as some people anticipate? I know when my parents had my younger brother, I was rather neglected....damn that little stinker!