Photozone have just published their review of the Sony A33. Generally, it's a positive review but I was a little surprised to see their comments on the high ISO capabilities of the camera which seem out of line with conclusions I've seen elsewhere.
My take is that 1600 ISO is usable, but that's all. My G1 at 1600 is quite bad in comparison. I guess if you use the multi-shot at 1600 ISO with the Sony, it's pretty good, but really requires a tripod for it to work well.
I was surprised because my take on the NEX5 which I believe uses the same sensor is that up to 3200 is fine and 6400 is a viable option when necessary. This was confirmed in the IR review which suggested 3200 could comfortably produce high quality prints at 14" x 11".
The NEX does not have the mirror to block some of the light and I guess that is the difference. I've shot some 3200 but they are pretty bad. Now I have the high ISO NR turned off because it's pretty strong.