After four years of moderate use, auto focus on my Sigma 105 macro failed in a big way with a horrible noise coming from the D90 when attempting to focus from distance to close up. I certainly wouldn't have expected a mechanically driven lens to fail like that after such a relatively short time. After much deliberation decided on a Tokina 100 and although it's early days I think it beats the Sigma in all respects.
My macro lens gets much of its use photographing moths on the sheet at night. The action can get pretty frantic and there is just not the time to use manual focus. The moths and the photographer are moving constantly, all shots are hand held, often in haste, and auto focus is the way to catch them. I do of course use manual focus when there is the time and need, small subjects in poor light for instance. In the work I do in the Australian bush there's a place for both. Cheers.
