I have a quad 2.93.
1) Nope, plenty quiet for me. Much quieter than my PMG5. No humming or anything. And trust me I notice little things. The chirping that the dual G5s made was pretty annoying. The solution was to disable NAP as it was causing fluctuations in the power supply which led to it chirping under certain power loads.
2) No problem with shutdowns. I have no idea what that problem is. It take about 5 seconds to shut down and I haven't seen any indication of a problem.
3) I don't use bluetooth so I can't say for sure. My understanding is there might be a problem with bluetooth mice. I don't have any problems with my wired mouse except in 1 program, but many others are now reporting it and they are on older core2duo iMacs and macbook pros.
The only problems I have are:
1) When the computer sleeps the display and I wake it, 90% of the time I am welcomed with a snow screen. I can fix it by cycling through the video sources (takes a couple seconds to do that) or just turn the display on and off. I will also get the snow if I cycle the display through the video sources and them go back to the computer source. It never ever ever ever does that when I start up, only when it sleeps the display or when waking the computer its self from sleep. It really seems like a driver or maybe firmware problem not a hardware problem.
2) If I look very very closely at the screen, in dark gray or grey/green areas I can see little diagonal lines moving across the screen, like a wave. It is certainly not the display as I still have my PMG5 hooked up to the same display via VGA and it does not show the same phenomenon with the exact same image (I tend to notice it easiest at the bottom left corner of the default desktop with the lines moving out from that corner). I'll contact apple if the problem persists after the next update. It really isn't noticeable unless you are about 3 inches from the screen so I can live with it.
So overall I don't really have any serious issues. I am very happy with my purchase so far. Considering I can run 4 QT movies, 4 WMV movies, play itunes with the visualizer, play 2 HD movie trailers in safari, have a game running in windowed mode, launch activity monitor and then use expose and still have 70% CPU idle... I am quite sure I did not need the 8 core model.
Edit: The snow of which I am talking about.