Jerome, as a long time Bigma owner I would not let the lack of HSM stop me from purchasing the Bigma. This lens works fairly well and fast with the screw drive in good light, of course, if silence is your need, then it might be a slight problem. In less than very good light the Bigma hunts like a coon dog, and HSM will not cure that I'm sure. It is a slow lens, and I prefer MF for most work. MF works well for me and many other Bigma owners I know, of course there are reasons some need AF .......less than perfect eyesight etc. I would be very unhappy with the Bigma if I had to depend strictly on AF, HSM or not. MF is very necessary witht the Bigma.
If you can live with this, the Bigma is a stellar lens, providing abilities and IQ at a very reasonable cost for shots you would otherwise miss.
If you go to my Galleries here, the first two, squirrels and birds contain (in the later pages) many, many, Bigma shots. Anything you see in the EXIF below the photos with a MM longer than 300 was shot with the Bigma. I post the good ,bad, and ugly in my Galleries, but I think that you can see enough good to realize the value of the Bigma. It is my avorite lens, no PF, no CA, no flare...just a good dependable lens that performs well wide open from 50-500 and everywhere in between. Many say it is an amazing lens....I cetainly agree.
I hope this helps you some, I was not expecting too much when I bought my Bigma a long time back, but it has amazed me from the start, and still does.
Also notice the shutter speeds on some shots when used with the K10-20D. With SR the Bigma is even a better value, allowing some shots otherwise missed.
James Williams's Photo Galleries at pbase.com
Here is a Bigma shot at 50MM..it is handy at every range.