Based on my personal experience a850 raw files are still good up till ISO3200.
Below shot is taken @ ISO3200 and processed with LR3. Ever since Adobe updated it's RAW processor, the weird colour smearing previously seen on Sony RAW files are gone
Yup with lr3 , all the noise gets eliminated mysteriously . Hence shooting iso3200 remains acceptable, but I keep to 1600 as much as possible heh