Update 05/10/08:
Asus Eee PC 900 on Buy.com and other stores, NewEgg still did not list the 900 again.

Update:
NewEgg delisted the Asus Eee 900 PC product pages again. Either Asus pulled them back or they published the pages by mistake. In any case the Asus Eee 900 is supposed to be in stores on the 12th.

NewEgg started taking orders on the new Asus Eee 900 PCs and the new Eee PCs are ready to ship.

ASUS Eee PC 900 12G XP and the ASUS Eee PC 900 20G each sell for $549.99.
If you prefer Windows XP you get 8GB less of flash memory. Besides that difference both Asus Eee PC 900 are the same.
NewEgg only offers the white Eee PC 900 notebooks.
It will be interesting to see how well the Eee PC 900 will sell given its price above $500. There are normal notebooks priced in that region available on the market.
The Asus Eee 900 PC shines through its small, but usable 8.9 inch screen, SSD storage and its compact size.
More details on NewEgg.