This is quick and dirty test that was done for no other reason than my own curiosity. However, I was quite impressed so I thought I'd share it. The *ist DL, with the 40mm f2.8 attached, was set to ISO 1600 - a sensitivity level that I normally wouldn't think of using on the K10D.
The unprocessed shot, taken at f2.8, is at the very top and shows the results straight out of the camera. That's a 6 mp jpeg at the highest quality setting that only had a slight levels tweak and was then reduced in size. The photograph below shows the same file after it was run through Imagenomic Noiseware Professional and a bit of unsharp masking applied. I think that shows that ISO 1600 is entirely usable on the *ist DL. You really have to click on the pics for the enlarged version to find out what I'm on about. I'm going to shoot the same pic with the K10D to see if there's much difference.
The other notable thing is the nice bokeh produced by the 40mm. It's maybe not the sternest test of bokeh but the lens has produced a very attractive background with no irritating double lines or excessively haloed highlights. I'm off to get some more handwash now :-)