The fan in my Thecus n2100 is too loud, so I'm getting a new one that's hopefully quieter. The fan is running full speed at the moment and its not blaring but I can hear it from the other room if there is no other noise.
There are reports that the thecus n2100 runs too hot, but mine has been at or under 40 degrees C so far. Those reports are with Western Digital (WD) drives, and I'm using 2 Samsung 500GB HD501LJ Spinpoint drives. Maybe that is the difference? (The room my Thecus n2100 is in is actually pretty cold right now so maybe that helps too.)
Here are some other comments about the Thecus n2100 fan.