It's a wonderful concept in my opinion, but the reason it's halted right now is probably because they were confronted with two problems:
1. A normal LED screen would consume too much energy, and so two OLED screens would have to be used, but that would probably be too expensive.
2. The battery would have to give the same 10 hour as the iPad to be competitive, and it's more difficult to achieve this with two screens and an Atom CPU that still hasn't got to 32nm or lower. The battery would necessarily be too bulky and too heavy.
But this is temporary; battery technology is evolving, the CPU is just a matter if time; and the OLED.. well. if the two first factors get taken care of, they might get away with LED LCD.