For over 30 years, I've shot everything with as low an ISO as possible, because image quality is important to me, but I experimented today with some shots comparing the same scene shot with ISO 100 and ISO 800 and couldn't detect any noise at the higher ISO.
This really impressed me, and I've adjusted my auto range to span 100-800, which gives me much more latitude during low light conditions.
Now I'm wondering how far I can go, and if anyone knows at what level of ISO the K20D starts getting noisy?