This is the same PRS-T1 that Sony launched in the US and Europe back in August. It's based on the latest generation Pearl E-ink screen, and it has Wifi, a microSD card slot, IR touchscreen, stylus, and Sony's excellent annotations features.
Reviews have put the T1 as being solidly in the middle of the field. It's a nice improvement on Sony's previous ebook readers, but it also doesn't have any amazing new features. Other that the annotation and the new on-device library ebook support the T1 has little recommend it over it touch screen equipped competitors.
The Sony Reader PRS-T1 is running on a well concealed version of Android, but it turned out not to be protected carefully enough. Last week I learned that the T1 had been hacked and that you will soon be able to instal Android apps. A week has passed and I don't have any new news, alas.
Retail is going to be 20,000 yen (~$262), which is considerably more than the $149 that the T1 is selling for in the US. (Don't you just love living in a competitive market?)
The announcement also mentioned that the 3G model I found a few weeks back is also coming soon. It's confirmed for late November with a retail price of 26,000 yen (~$342 USD). According to Sony, the G1 will only be available in black and white. It's going to have similar hardware specs to the T1, but it's also only going to be released in Japan.