Not too long ago, I wanted a fast telephoto zoom, but I didn't want to lug around a 70-200 2.8 lens. I instead chose the relatively compact Sigma 50-150 2.8, which, along with the Tokina 50-135 2.8 and the similar Pentax 50-135 2.8, are currently the only crop-sensor equivalents for the 70-200 2.8. The Tokina 50-135 has been hard to find for a while now, leaving the Sigma 50-150 as the only viable option for non-Pentax shooters. I was able to get one, which I reviewed here: http://betterfamilyphotos.blogspot.com/2010/09/sigma-50-150-is-tight.html .
A few months ago, the Sigma 50-150 was reportedly discontinued, to the chagrin of its many fans. Many people - myself included - assumed that Sigma abandoned the 50-150 to focus on selling the 70-200. Indeed Sigma recently dropped the price on its 70-200 2.8 OS to increase its sales.
About an hour ago, Sigma issued an announcement to release the replacement for the 50-150: the redesigned Sigma 50-150 2.8 OS. I'm speechless! I'm a fan of the Sigma 50-150, although I found it sometimes challenging to use without stabilization. Although it seemed that adding stabilization was technically possible, I assumed that Sigma wouldn't produce a stabilized version because it would drive up the cost. Well, Sigma has proven me wrong, fortunately. With stabilization, the Sigma 50-150 becomes a formidable option for crop-sensor cameras. Based on the stabilization performance of other Sigma OS lenses, I'm confident that the OS in this lens will be effective. The only question is how much the new lens will cost.