My guess is that the 15-30 would follow along the lines of the 24-240 and 16mm in having large distortion and heavy vignetting at the 15mm end, requiring software correction. This usually means that even stopped down to f8 (assuming that produces the best optical performance), the corners would still not improve much compared to wide-open. The distortion and vignetting may not reduce to 'acceptable' level till about 16-17mm, making this effectively a 17/18-30mm lens. At the same time, the optical quality could well not be high enough to compensate the software-corrected corners, unlike the 14-35L, which also have heavy vignetting and strong distortion at 14/15mm, but the optics are good enough to allow software-corrected corners to still be pretty good. Nevertheless, if I were to take this as an 18-30mm lens with good to very good optical performance, and if it is light (300g?) and that the price point is good, say, $400, then this could be an attractive option (for me).