Pentax has always been a bit of an oddity in the camera world. Not as big as Canon or Nikon, but not small enough to go out of business. Whilst their cameras have always been solid and reliable, their lenses have always been very impressive and the 50mm f/2.8 is no different.
As with all prime lenses, the quality of image is top notch. The colours are sharp and reproduced very well, if not a little soft at the wide open end of the lens. With a maximum aperture of 2.8, it is operational in fairly low light conditions. It is probably best used for portrait photography - I certainly did and it served me very well. The wide aperture produces nice bokeh for this purpose. Furthermore, the lens is also fairly light at just over 300g and is small enough to slip in to a large pocket to carry around.
Like all Pentax lenses, the 50mm f/2.8 is solidly constructed and I have had no qualms about carrying this around with me at all times. If you shoot Pentax, this is great purchase if you can't afford the f/1.4 or f/1.7 alternatives.