hate to repeat, but it really does depend on what you are going shoot... if you need the flexibility to be mobile, the IS is invaluable. if you can setup some make shift "shooting position" (be it tripod, wall, or someone's shoulder), you can afford to save the $1k on the non-IS version.
controlling our cam handheld at 200mm without IS can be pretty difficult, even if you can get high shutter speeds exceeding 1/250.