I am going to Alaska next summer and want to get a telephoto lens for my Canon 50D. I am looking at the Sigma 150-500 lens with OS. The Canon 100-400 is a bit outside of my budget, but am told that the Sigma quality control in not consistant. Has anybody had experiance with the Sigma lens?
Though I don't own this particular lens (I also have a post seeking info on it) I have had many Sigma lenses over the years and have always had good luck with them. I currently use their stabilized 18-200mm for most of my photos and am very happy with it. You can find a review of the 150-500 in the equipment section of this site.