To be honest.. I didn't hardly hear a thing when it focused right away. I was in some very dim light shooting the cats.. non-contrasty subjects and all. So it did "hunt" once or twice... Noticeable, but very quiet... not bad at all. The only lenses I have that are quieter are my 70-200 2.8 VRII and my 24-70.
I did take some low speed (40) non-flash shots.. and they look pretty good. I took this standing off hand.... with OS 2 at Shutter Speed of 40, F6.3, ISO 800 in a fairly dim room lit by fluorescent and incandescent light. Left the Exif in it so you can check it.