I just picked up a Sigma 19/2.8 and as I am playing with it I have started to wonder if Sigma lenses are actually good or are they simply benefitting from the fact that there aren't a whole lot of affordable lenses for Sony. So let me be clear to start this off, I don't think the Sigma 19 is a bad lens at all, but I am wondering if it can really be called a good lens? It's kinda slow, the AF is decent, the build seems durable (unlike the Olympus 45/1.8) and the IQ is perfectly serviceable. Clearly the Sigma 19 is capable of producing nice images but I also think the main reason that folks buy it is because it's cheap. That's why I bought it and with that in mind I would say I'm happy with the purchase. Admittedly I only have experience with the Sigma 19/2.8 and 30/2.8 (on m43 and E-Mount) and while I never regretted having them I can’t say that I would specifically choose to use them over any other lens. They were always the default choice when I needed AF. So, are they good? If you have a Sigma lens do you like it and is it for reasons other than it being affordable or the only option out there?