I have the Sigma 150mm macro without OS. One the one hand, I'd love to have the OS, but on the other hand, I've never missed having the stabilization. I should note however that I almost always shoot with the lens on a monopod, not so much for the stabilization, but to take the weight of my hands and wrist, if I"m shooting long. Needless to say, the monopod adds stability to the camera/lens platform.
The longer reach if shooting bugs is a nice feature, if you're shooting florals, you don't need 150mm. The bokeh on my currenct lens is excellent. This lens is slowly becoming the "go to" lens for many, saving money over the longer Canon 180 lens, with basically the same quality except weather sealing.