Although the Sony Alpha has not has not been released, it has been reviewed by www.trustedreview.com. I assume its a pre-production model.

They conclude with:
“An extremely impressive debut from a new player in the digital SLR market, the Sony Alpha α100 is pitched at the consumer end of the market, but is actually a better camera than most of its mid-range rivals too. It bristles with clever technology, but is very easy to use and produces consistently excellent results. It would be a good camera for a newcomer to SLRs, but more experienced users will also find it very satisfying to use “

Interestingly, the noise level at ISO 1600 is high and writes “At 1600 ISO the image is quite noisy despite the very fast shutter speed. It’s no worse than most of its rivals though”. That is, in terms of noise it’s on par with the Nikon D200.

Source: Trusted Review