Being an owner of an 360 I can safely attest to the fact that the dang thing sounds like a small plane warming up it's engines.
The really sad part is my computer is an AMD 4200+, with 2 120mm case fans, 1 90mm side panel fan, plus the CPU, GPU, and PS fans, and it's maybe 1/4th as loud as the 360.
But my thinking is that if the PS3 has the same heat dissipation problems displayed by a 2.8ghz Intel or AMD, and the G70 is comparable to a 7x00 card, these things are going to cook themselves fairly quickly. The smaller the fans, the louder the noise with bearing models, and if these things are quiet they may not have adequate cooling. Sleeve model fans are quieter, but the price is that they have high rates of failure and relatively low lifespans, as well as problems with odd orientations, like being mounted horizontally and then turning the case so they're vertical. Something with balancing causes unusual wear.
I just don't see how Sony, who's never manufactured a modern CPU/GPU is going to avoid all of the problems plaguing the Pro's. Especially in a poorly ventilated case(by comparison).
Don't misunderstand me, I'm not "Sony must die!!!", I actually like BR as the HD solution better. But I think their console division isn't playing with a full deck and has gotten arrogant, thinking they don't have to play by the rules everyone else follows. I really think the PS3 is going to bite them in the butt.
Honestly, I'm sitting here looking at my 360, who's case is filled with holes for heat disipation, and knowing the fans blow very hot air out of the back. Then I'm looking at my computer, and knowing the temps in my very well ventilated case are ~90f on a good day at an idle(MB, CPU, GPU averaged). And I can't figure out how Sony's going to avoid all of these problems.