5 out of 10 points and recommendedlight weight, wide range of focal length, great travel lens for reasonable costnot great for low level light, significant vignetting at wide angle and low light, looses significant sharpness at larger aperatures
I have always enjoyed the Pentax film cameras and was pleased when the K10D arrived (I went Canon 20D because I wasn't sold on the early Pentax DSLRs), allowing me to use my Takumar lenses. However when the Pentax 18-250 came available I thought it would be great to cut down the weight and the lens switching. To date it has served well as a travel lens but returning from recent trip to Europe and processing over 1000 images I began to notice that low light wide angle shots (lots of these in the narrow streets and indoor museums and galleries) that the sharpness suffered and vignetting was significant. Also, the lens hood has become difficult to put on and off as the two plastic surfaces seem to bind on one another.reviewed December 10th, 2008 (purchased for $525)
Since I still have my Takumar lenses I did a series of test shots comparing the two lenses. (Takumar 70-200 and the Pentax 18-250)
At 70mm and max aperature the Takumar is significanlty sharper, no vignetting on either lense
At 100mm difference in sharpness greater
At 200mm the difference even greater again
A similiar test comparing Takumar 35-70 with the wider angle focal lengths on the Pentax 18-250 using focal length at 35 and 70mm showed in addition to less sharpness on the 18-250 but also significant vignetting.
Overall, for travel I will continue to use the light weight combo of the 10D and 18-250 lense (3lb total weight) and avoid extreme wide angle and large aperature use as much as possible, however, for more serious imaging I think I will stick with my Takumar lenses, At least until Pentax offers a series of higher quality lenses I will put off my upgrade to a K20D or newer Pentax camera or possibly consider a move back to Canon or perhaps consider Nikon.
Similiar test images using my Canon 18-85 f4-5.6 and the EF 70-200 F2.8 showed slightly better results that the Takumar. The Canon weight and bulk makes it less attractive for travel.