Excerpt: This lens makes a great general purpose lens when zoom is not required. The quality is a bit better than your average chinese made, panasonic lenses for micro four thirds systems out there. It is light weight and compact.
Pros: Consistent Output, Durable, Fast / accurate auto-focus, Lightweight, Strong Construction
Summary: I received this as a birthday gift and immediately began using it. My observations are not scientific but those of an artist and fine art photographer. The lens is crisp and focuses very close allowing me to do beautiful closeups. I am sure I would be able to do true macro shots with the aid of an adapter. but the point is that this goes in very close. It is very modern and sleek in appearance and the focusing ring is nimble and easily moved without being loose.
Summary: This was my first prime lens for my E-PL2 in the native M4/3 format to get away from kit zooms. Soon afterward bought its larger 60mm DN cousin. I've since upgraded to an E-PL5 and this is still my most used lens. These sigma lenses are crazy sharp with great contrast and color rendition, superior to kit and to other SLR primes I've used with a M43 adapter.
Summary: Works with the Sony Nex automatic focus/imaging system. It's non IS, but that doesn't matter. When you want to use manual focus, it's focus ring is grooved and it turns smoothly. This lense is short and allows good images, as long as it's not used for Moon shots. It has dropped in price to about $150, the last I checked. The replacement is called an ART lense and that lens is $200+.
Summary: This is a typical Sigma: not the original brand, but still very good construction and optics. I was lucky to get these in a promotion for $139. It's impossible to find a 19mm F2.8 with the same quality at this price. Notice it is not a VR Lens (Vibration Reduction), but again, for the price it is a bargain, even at $199 as it is today.