The 28-135 offers significant improvement in image quality over the 28-200 at the long end. At 28mm the 28-135 will provide edge to edge sharpness, that the 28-200 does not. If it is worth purchasing is only a decision you can make. You might consider the Tamron AF 17-50mm F/2.8 XR Di-II LD SP ZL Aspherical (IF) Zoom Lens instead for a wider lens. I picked up the Tamron on ebay for $325, which is similar in price to the 28-135. The Tamron's auto focus is a little noisy that is my only complaint. Another great wide option is the Canon EF-S 15-85mm f/3.5-5.6 IS USM UD Wide Angle Zoom Lens, I don't own the 15-85mm lens as I couldn't personally justify the price, as I am happy with the 28-135. The 28-135 is the lens I keep on my camera as my everyday lens, and switch to my other lenses as needed.