Would you mind telling why you like it so much and how you are using it? I got one a while back thinking it would be on the camera most of the time but it rarely comes out of the bag.
OK. I have many lenses, like most other Pentax users- several limiteds, which are awesome, old Russian lenses, Cosinas, Rokinons, other Pentax primes and zooms (LBA

). But I see a niche for a walk-around lens that I don't need to take off the camera at whatever event or location I happen to be (e.g. what if it's dusty or wet?). Sure, I could choose a prime to walk around with, and I do that sometimes too, or for that mater multiple cameras, but luckily I'm not a pro who has to load up on gear, lol. I have for years been using a Tamron 17-50 2.8 as my fav walk-around lens, and it is a great lens for that. This lens, although slower, is superior to the Tamron in many ways. Way better close focus capabilities (0.26x), it's sharp wide open and overall better edge-to-edge than the Tamron. It is quiet and it's weather sealed, and resists CA better. And it has more reach at both ends. The build quality is very high. Hence, a highly useful lens for me, and I'll be selling the Tamron. Plus, it is on sale right now...
Do you do astro or birding with your Bigma and 1.4x?