Sounds like an interesting lens. It is said to contain a UD element for better optical performance, and the IS will be a nice feature. It will give users an equiv. FOV of a 400mm lens in 35mm film.I am tempted to replace my 70-200 f/4 L with this and get a 300mm f/4 or 100-400 L for longer reach, but only if the 55-250mm has reasonable optical quality.