For product itself:
The "first" robot is built quickly, but relatively unspectacular. Quick can be extended with the software supplied with the standard robot and programming.
The programming is easy to understand relatively simple and probably also for the younger ones.
My really only complaint is the poor extensibility of the NXT unit.
If you want to grow more than 4 sensors or 3 servo motors, it becomes difficult. So far I have not found a way, without having to buy a second, expensive NXT unit.
Fun: 5
Educational: 5
Durability: 5
General: 4 (precisely because of the poor extensibility)