After reading some of these posts, it sounded like a different lens than my Tamy 28-75 f2.8 to the extent that i took it out to see if it had turned into a Frankenstein monster
a. Noise - I never regarded the Tamy as noisy compared to the snap of the K10 and 20 shutters. I'm pretty sensitive to noise, but the little scrunch of the Tamy has not bothered me. I think the K5 being so quiet has emphasized the Tamy, perhaps.
b. Hunting - huh. My Tamy doesn't hunt and is very sharp. Esp with the K5, it focuses fast enough IMO. One thing that helps a lot is to deactivate the half=button focus and activate the AF button. When i do stage plays, i usually only focus every 6 shots or so. I use a the widest dof i can get away with according to the light, like a f5.6 to f8. With the wider depth of field, i don't need to focus so often.
c. I also find it makes a good walk around lens, but i like to use my DA-21 for a wider angle in crowded sidewalks.
at times i wish i had the wider 24 of the Sigma equivalent, but i don't expect to get rid of the Tamy anytime soon.