Good point on shake reduction
Ivan's point is worth calling out. UNLIKE Canon and Nikon, Pentax puts shake reduction in the camera body. Thus, 30 year old lenses work with shake reduction turned on. And brand new lenses can be smaller and cheaper than an equivalent Nikon and Canon lenses which must put shake reduction inside each lens. There are advantages and disadvantages to each system, as with everything in life, but the original big advantage of putting it in the lens is that it worked with 35mm film cameras (before digital even existed). That advantage for Nikon and Canon is now gone and more of a historical decision they continue to live with.