The MTF curves suggest it will be sharper, focus will be quieter too. I'd say it's a step up, definitely - but if you want better IQ and don't plan to shoot a lot of video with AF, the 17-55mm f/2.8 IS USM or 15-85mm f/3.5-5.6 IS USM offer the best IQ in a general purpose zoom for APS-C.