Apparently I had better luck with this than previous reviewers. The press definitely cubed my eggs, although the edges and corners were slightly rounded--they looked like big dice. Here's what I did: I used "old" eggs that I'd purchased a couple of weeks ago, because older eggs are easier to peel. I steamed 6 eggs for 17 minutes (I prefer to steam rather than hard-boil because there's no bouncing around in the pot). While the eggs were steaming, I stuck the egg cuber in the freezer and filled a big bowl with ice and water.
When the eggs finished, I peeled and cubed each egg one at a time. I noticed that if the eggs were still hot when I decanted them from the press, the egg would spring back to a more rounded shape, so while each egg was inside, I dunked the bottom part of the cuber (up to the bottom edge of the lid) into the ice water for 1-2 minutes. Then I decanted the cubed egg, put it on a plate, peeled the next, stuck it in the cuber, dunked the cuber into the ice water, etc. I was able to cube all six eggs with no problem. The last egg was plenty hot when I cubed it, so probably I could have cubed more.
The longer the press was dunked in the ice water, the better the eggs held their cubed shape. I'll probably experiment to see if I can get the corners and edges sharper, but with the above procedure, the eggs were cubical enough to surprise my kids.