In reference to the A200 improvements in higher ISO speed noise levels, here are samples from Dave Etchells at imaging-resource.com
Click on the image that loads to see the full size 10 Megapixel Original.
Sony DSLR-A200, ISO 1600, 1/250 second, 70mm, f/8:
The A100 did not have an available ISO 3200. But, it's there if you need to use it with the new A200.
Sony DSLR-A200, ISO 3200, 1/500 second, 70mm, f/8:
Looking at a full size 10MP original size image on a typical monitor is looking at a poster size print from up close. ;-) So, keep your desired viewing and print sizes in mind when judging image quality.
We should start seeing a lot of real world photos from this model soon, too (it's shipping now).