Quite honestly I think it's going to be around $750 to $850 street. That's at par with Nikon 18-200 VR lens. However, once you use IS, you'll never go back.
IS (Image Stabilization), especially the new ones can give you up to 3-stop advantage. So if usually you need 1/30 sec shutter speed minimum for a wide-angle shot, with this lens you can bring the shutter speed down to 1/4 sec. This is especially useful in zooming. At 200mm, most people will need at least 1/200 sec shutter speed. With this lens, in real life application, you can bring the shutter speed down to 1/50... or even 1/25 (in theory).
Obviously I've never used this lens because it doesn't exist yet, but with my 70-200 IS, I've been taking pictures at 200mm focal length at 1/60 with zero blurring.