a rather recent discovery for me after being attached to my DA15 for a couple of years, the DA21 is every bit as good in quality as the 15 and has become my default wider lens. I always figured i could zoom with my feet to fill the gap between DA15 and FA31 but I had a few situations where that was impossible and I was holding the wrong tool for the job, so this guy caught my attention.
Knowing that technology dictates a faster lens is typically larger in size, i'd much rather save the space in my kit than have something larger for reasons i'd never utilize. As I am primarily a landscape shooter, I cannot relate to the comments that it is not fast enough, as I would never use it below f/8 anyhow, and it is faster than the DA15. So small, that both lenses stack in the same pouch on my photo vest, so they are always at the ready. I bought new from Adorama and got a good copy right off the bat, no focus issues, no IQ issues, etc.
I do wish ALL pentax lenses were WR and would probably pay a premium for that, but i get that not everyone needs this feature. Overall hightly recommended!