The PRS-G1 looks to be the same device as the PRS-T1 (which just started shipping here in the US). It has the same 6" Pearl screen Neonode IR touchscreen, Wifi, card slot, etc. But it also has 3G in addition to the Wifi connection.
According to the product page, it's going to be available in late November in black and white (but not red), and there's no sign that it will come to the US. This is something of a surprise. Sony have shown signs of not being able (or willing?) to innovate anymore. They followed the pack with Wifi and price and by dropping 2 of their 3 models. But now they have a 3G equipped Sony Reader. Maybe I counted them out too soon.
Do you know what? Given that it isn't due out until November, I think there's a good chance that we might see it in the US. I'm still waiting to hear back from my contacts at Sony, but that long delay in the release date suggests this product page was a leak.
If this does get released in the US then it will be the Kindle Touch's only direct competitor. Sony could do quite well in that particular niche.
Update: I've heard back from Sony and it's going to be available only in Japan.
It’s probably easier for them to get a 3G arrangement in Japan than here. I don’t think they have the numbers to get the kind of bulk 3G discount Amazon gets.