My 60 GB PS3 the hottest and loudest of the bunch. Every model after that has run cooler (more energy efficient chips built from newer technologies), and quieter. That said, I have my PS3 on an open shelf right under the TV, I can't hear it from 7 feet away in most cases. Blu-ray playback is no issue at all, it takes very little of the PS3's power to decode Blu-ray video and the fan runs at the lowest speed. Actually some DVDs with very noisy pictures, can get the fan running up to an audible point when noise reduction is enabled. Games will also sometimes get the fan running so it becomes noticeable.
The other problem with fan noise on older PS3s, is they are full of dust. The fan has to run harder and more often to cool them in this case. Taking it apart, removing the dust, and also replacing the thermal compound between the CPU and heatsink, got my system running quieter than when it was new.
