I personally own the Jetbook, but am about to return it to Ectaco, to get a $100 cashback deal on it for buying the JBC. From that $100 I'm basically buying the Aztak, costing me only $50.
At first sight I would gain:
1- Whiter background
2- E-ink (longer battery life)
3- Higher resolution (640x480 for the jetbook, to 800x600).
The way I see it, they are all wins!
- Customer support,
- Screen response time
and seemingly also:
- Some file compatibility
Though, I'll mainly read txt, and epub on it.