Well I had the 60-250 and that is a very nice lens:
DA*60-250mm/f4
I sold it to buy Sigma 70-200mm/f2.8 EX DG OS HSM and that is also a very great lens. I also was in some need to use f3.2 and f3.5 but I like this lens the best at 200mm and f4.
I also bought DA*300mm/f4 since I missed the extra length. The difference between DA*60-250 and DA*300 wasn't big enough, but the step from Sigma to DA* is good. I use two camera body's.
The Sigma is with 200mm/f4 sharper then DA*250mm/f4 and the DA*300mm/f4 is sharper then 250mm/f4.
The Sigma lets a little more light in then both Pentax lenses did (to my feelings, since I didn't measure it precise) so I overexpose the DA* by 1/3th stop to get my image. Offcource this is seen back in either iso or either TAv-setting. Depending on the amount of light available.