Hi, I am out of Udaipur for some days now and give a more detailed report later but basically I love this lens and especially on the K5. Once I get back home to Udaipur I can try it on my K10 as well.
The lens is quite heavy but anyway easy to use without tripod. Actually, I have not even used it with tripod yet. I mostly use it with the optical stabilisation in the lens as it also helps in the view finder.
The lens is very sharp and I usually get better results from this at 50mm than my 16-45 4AL at 45mm (in terms of sharpness).
I don't have that many pictures online from this lens yet (besides on facebook) but here are some samples:
ISO 3200. 500 mm @6.4
My first shot of the moon
500 mm
This picture is perhaps not very good but it is a 100% crop, unsharpened and unaltered. The building is 4.5 km away and you still see the cables. Weather was not perfect and we even had a light drizzle at the time. So I think it is quite amazing anyway. See map for details.
With a High ISO monster such as the K5 it is actually working quite nice for low light indoor pictures as well. These are from an Odissi dance in Udaipur. No posing but actual dancing!
I think I paid rs 80-90k (been some months now so I can't really remember) for the lens with international warranty. You get a strap and nice (and big) bag with the lens the fit the lens with attached hoods.