Overall, it's a solid performer. This review confirms the finding of earlier reviews. The weaker point of the lens is corner sharpness at wide angles. While not terrible, it underperforms here, e.g. compared to the Sigma 28-70 at 28mm:https://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=1646&Camera=1538&Sample=0&FLI=2&API=0&LensComp=1566&CameraComp=1538&SampleComp=0&FLIComp=0&APIComp=2

SamKnopf wrote:Overall, it's a solid performer. This review confirms the finding of earlier reviews. The weaker point of the lens is corner sharpness at wide angles. While not terrible, it underperforms here, e.g. compared to the Sigma 28-70 at 28mm:https://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=1646&Camera=1538&Sample=0&FLI=2&API=0&LensComp=1566&CameraComp=1538&SampleComp=0&FLIComp=0&APIComp=2I don't see much difference above. Doubt you can tell difference from real-world photos after sharpening.But then Sony leads obviously at 70mm. The difference certainly is much more than above.https://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=1646&Camera=1538&Sample=0&FLI=5&API=0&LensComp=1566&CameraComp=1538&SampleComp=0&FLIComp=3&APIComp=2I used to own Tamron FE 28-75 G2 (sold to prepare for this lens) which is slightly sharper than Sigma 28-70 overall that can rival Sony GM II according to some reviews. But from what I have seen this new Sony lens is very close to Sony 24-70 GM II and even edges out at specific FL such as corners at 70mm.  20mm is much wider than 28mm that makes this lens is more useful.  One-stop difference is not a big deal as I use fast-aperture prime lenes for indoor hand-held photos such as 14 GM, while put on tripod in low-light outdoor.I will get this new Sony lens and I am quite happy on its spec and performance I have seen so far.