I use the previous model Sigma 150mm f/2.8. The new model has OS and I'm sure that would be useful for shooting things other than macro, but don't know how effective it is for macro shots.
My lens is very sharp for macro and for non-macro shots and the AF is pretty fast when using the distance limiter. Here are some sample shots with the older version and the new model will probably be even better.
Canon 30D - 1/3200s f/4.0 at 210.0mm iso400 (I used a 1.4x teleconverter for this shot too.)
Canon 7D - 1/1600s f/5.6 at 150.0mm iso200
Sigma has a lot of lens they designate as "macro", but most are not 1:1 macro lenses. The 150 is.