Hey guys... sorry for starting another 70-200mm comparison thread, but unlike most others, I'm going to be very specific about my needs and how I want the two possibilities to be evaluated... First of all, you all were VERY helpful to me when I started a thread asking if I should consider the f4 version or the f2.8 version of the canon 70-200. Based on my needs, the clear verdict was to go ahead with the f2.8. Now, I would like a question that has probably dogged photographers for a while: is the image stabilizer (IS) in the 70-200 f2.8L IS worth the $500 premium over the non-IS 70-200 f2.8L? As in my prior thread, I would like all of the comments and suggestions to consider the value of the IS vs. the non-IS. What this means is that I would like the suggestions to consider cost vs. benefit and suggest what they would consider to be the maximum value given my requirements. Comments like "Get the IS because it's better." don't help me. I realize that the IS version has a feature that the non-IS doesn't and that makes it better. But does that make it $500 better, is what I'm asking. Money doesn't grow on trees! My requirements: This lens will be used for 80% weddings, 10% portraits, and 10% indoor sports. So mostly weddings. Pictures will be 99% handheld. Weddings are very fast-paced and I rarely have time to set up a tripod to capture moments that may last for only seconds. Every wedding I've ever done has had challenging low-light situations, which is why I'm opting for the f2.8 100% of the pictures will be of people. No architecture/landscape/other photography here. Cost is important and $500 is a lot of money to me. The longest lens I currently have is the 28-135 f3.5-5.6 IS. I need to upgrade because I need a lens with a higher maximum focal length (for ceremonies where I need a long reach to capture details without being in the way), is faster (for low-light ceremonies and receptions), and has better bokeh and higher image quality. That's why I decided that the 70-200mm f2.8L is a good fit. But do I really need that IS? OK, I know you guys will have lots of useful things to say, and I thank you ahead of time for your help!