Hmm, I'm surprised why this lens isn't getting the attention it deserves. This lens is the crop factor equivalent and replacement of the popular 70-210mm/80-200mm tele zoom in 35mm film format.
Having had a brief tryout, to me it is a fantastic lens, I dare say even better than its DA* 16-50mm counterpart. The benefits of the SDM is even more apparent on this lens than on the wide angle DA*. The lens isn't heavy and very well balanced plus it is weatherproofed. SDM is the way to go for long teles and tele zooms. Focusing is way better in terms of speed and quietness compared to screw drive AF. Images come out very sharp and show great contrast, perhaps better than the traditional 70-210mm/80-200mm f/2.8 tele zooms as it is optimised for digital.
The traditional 70-210mm/80-200mm range is really too long with the 1.5x crop factor (approx. 100-300mm in 35mm format equivalent). Even in 35mm film format days, most camera companies and third party lens makers didn't sell very many 100-300mm zooms compared to the popular 70-210mm/80-200mm zooms. And most 100-300mm zooms maxed out at f/4 (like the Tokina AT-X), not f/2.8.
My only grouse is the pricing of this excellent DA* lens. Here in Singapore, the Tokina 50-135mm equivalent for Canon & Nikon mounts sells for almost half what the Pentax is going for.