I'd give them 3.5 stars. These are really overpriced for what you get. The dice are foam, and seem unlikely to hold up long term, and the plastic pieces are quite thin and feel kind of cheap. In fact, they are so thin that sometimes my son has a hard time telling if the tower is 34;flat34; or not, which is kind of the whole point. However. It's a great idea, and I haven't seen anything else quite like it on the market. I love math manipulatives, and I think with a few adjustments (like thicker pieces, and I would argue for uniformity of color to isolate number as the important characteristic) these could be really great for classroom/homeschool purposes (which is why I originally bought them). The game itself is fine, but there are lots of other things you can do with them - to start with, I just had my son build towers with a ten as the base. He quickly began to think of 10 as 1 and 9, or 4 and 6, etc., and he has gained an intuitive understanding of basic addition from this. They also give a great visual for even and odd numbers, as the even pieces are rectangular and the odds always have one protruding from a rectangle. I give it 3 stars because I think with a limited budget that a person should go for something like Cuisenaire rods, a number line, etc., and just use some paper 10 frames (you can search and print these for no cost). But if you are a early math tool junkie, then these should be in your collection.
Rating: [3 of 5 Stars!]