They LOVE them. On Christmas morning Kaden built a truck and Spencer built a bird house. They were able to do this with very little help from us.
A few weeks ago Spencer started dragging scrap wood from the garage and carrying it into the back yard to "build a house." He had them all lined up and then nailed the pieces together. It was very stable but he loved doing it.
I also bought them some scrap wood at a hobby store. With these pieces they made a box (which I don't have a picture of). With the left over pieces they practiced their hammering skills. The above picture is Spencer's piece. He did these completely on his own. And then Kaden practiced as well. He doesn't quite have the strength to hammer the nails all the way in yet. But he loves it still.