I had a first gen Macbook that I had for about a month (I was getting those random shutdowns and gave up), and my sister just purchased an SR Macbook this Friday. I was in charge of setting it up for her, and it seemed noticably cooler than the CD Macbook. However, the fan was running a bit more especially on AC, and quite often sped up to very audible levels.
I'd expect decreased heat cause of the new vent design which really helped the MBPs, but like I said I heard the fan a surprising number of times.
It's funny though you realize how anal you are when I'm disappointed that the fan is audible and my sister responds with "of course it's a computer"