A good buy if you need the versatility of a single lens. While you get convenience without loss of quality, it also feels a little heavy on the front. Equally you don't get the full light capture of a 1.4 prime from sigma.
It is superb. Supersharp, superquiet. The image quality is quite mindblowing. With an a6000 or similar provides a very compact setup, optically equivalent to but much smaller than a fullframe with a 24-70 f/4.
It’s a tad expensive.