TrustedReviews.com had the opportunity to test drive the Sony Alpha DSLR-A200 recently. A number of test were run including ISO performance test, details and exposure test.
Accodring to them:
At 1600 ISO the noise in the darker areas is very visible, and the noise reduction has softened the detail somewhat.
At the maximum 3200 ISO the noise is a lot more noticeable, but the sharpening algorithm has tidied up the edges of the black lettering.
Full in-depth review by Trusted Reviews of Sony Alpha A200 Digital SLR