I asked my 4-year-old what she thought of this Duplo product and she said, "It was fun."
She likes to match the numbered bricks with the corresponding bricks that have the same number of symbols on (like matching the number 6 brick with the brick with the 6 apples on and the number 7 with the 7 flowers etc.). Then she lines them up, or builds them up, in numerical order. And that is the educational part of the toy to which my only gripe is that the symbols can't be split up so sums are not easily doable. But you can work around that.
Also the toy can help with motor-neuron skills, especially of younger children in the 2-5 age range of the toy.
As well as the numbered bricks there are many other bricks (58 in all), including a dog and a man, and an instruction book which has some ideas in it for number games you could play with the bricks or things you could build with the bricks (the box says it has 10 ideas and 6 activities in). We've just built the little house and bed for the man and put the stars brick on the roof to indicate night-time. My daughter has just taken off the stars brick to make it morning time.
Lastly the Duplo bricks are of course compatible with other Duplo products so can be combined with bucket sets, say, and the bricks are highly durable as you'd expect. They'll last for when my next daughter, currently 4 months, is ready to play with them.