I just bought one of these last night at the Sony Style store here in San Diego, I'm getting a lot of low level hiss on the audio in a quiet room its quite noticable. I'm curious if your unit has the same issue. I'm going to see if I can exchange it for a new one this morning.

Update (4-27-2006)

Packed up the system and headed over to the Sony Style store. Played with the display model to see if it also shared the high audio noise floor. It did. They were very nice to give me a full refund, even waived the restocking fee. I hope this is an issue that is limited to the first wave of units from Sony, I really don't think I was expecting too much, the problem was extremely obvious on all the test clips we tried. Only did testing in the highest quality MPEG mode. Doesn't appear to be hard disk noise, its pink noise on both channels and is very obvious on both channels in a quiet room. Maybe the mike preamp circuit they chose is noisy? Using the reduced audio gain mode on the camera didn't really improve things, pushed the pink noise down a bit, but still quite obvious.