Andrew,
I have the 3HP Gorilla in a relatively smallish shop (approx. 1 1/2 car garage). It's about as loud as any other tool (less than the DW735 planner though) but not more so. I leave it on for more than 10 minutes at a time w/o hearing protection without being uncomfortable. And the most important measure is that it's not to loud for SWMBO sitting in the house fairly close to the garage. :)
Performance wise, it's great.
Chris