This lens is another walkaround, although maybe barely some might say, since in crop sensors its not longer 24-135mm. I find that for the great outdoors 24mm is quite good. But you might miss the wider angles, especially on walkarounds in the city.
The 135mm do for me more than make for it. As it allows to get more details out of the subject you are faced with. Its also good for picking up people in a crowd.
The build quality is well above the average, the lens feels very solid and sturdy. The focus ring feels good, but not smooth. The zoom ring is a bit harsh.
At 24mm and F3.5 its a bit disappointing, but if you stop down to F5.6 is pretty good. I was very well surprised by the sharpness at 135mm. Overalls sharpness is very good, on par with a 17-70mm except maybe at the sweet spot of the lens.
This is a lens from the film days, therefore it is full frame. If Pentax ever goes full frame, this lens will be and even better range.
The lens is on the big side (for a 135mm maximum focal length) and has a wide filter size. But this works to make it feel sturdy and a quality build rather than be a nuisance.
General prices seem too high, I would advise looking for a used copy.