The DA-12-24mm F/4 is really awesome and I use it quite a bit.
I have also used the NIkkor 14-24mm F/2.8 on a D3 and got some awesome results. It is true that many people do not know who to use such a wide-angle but that does not mean the lens should not exist. There are even more people who do not know how to use their cameras!
It has to be rectilinear for me (and for my clients), fisheye images do not sell that much (of course, some of anything do). I used a rented fisheye (on Nikon, they do not rent Pentax lenses here) and it just does not give results that I personally like (I know some people love them).
I'd buy the Tokina 11-16mm if it was available for Pentax and considering I paid $1600 for the DA* 60-250mm F/4, I would pay $2000 USD for a DA* 8-16mm F/4. More even it is F/2.8. There you go Pentax, that's how to get another 2K from me!
- Itai