Ah well Anel-slo, I blush to admit that I was so desperate to get a shot 'in the can' to fulfil this months task and being afraid that the light would change, that I just grabbed the camera and banged off a series of 5 shots (using the exposure auto-bracketing feature) quite forgetting that I'd set the camera to 1600 for a low-light shot the previous day. Had I had my brain fully engaged I'd probably have chosen ISO 400 as providing a decent balance between sharpness, lack of noise and lack of shake.
This particular subject with its large flat areas of mid-tone is especially prone to 'grain' but experiments with the Pentax K20D have shown it to give pretty uniform image quality from ISO 200 upwards to 1600. The 3200 option is very 'noisy' and I'll only use it if really cornered.
I did some tests a while ago when the kit was new and I was assessing its strengths and weaknesses. The link below takes you to a frame that should be self explanatory, I haven't been shy of using 1600 since.