My oldest son and I eat a lot of hard-boiled egg whites. Last Xmas my daughter bought something similar to this for us. It didn't work for us - too hard to see it in the water and it smelled really funky - hated to think it was seeping plastic chemicals into our eggs.
We also got an electric egg cooker (it was kind of a joke - everybody got a "kitchen" present based on their eating habits). It does make good eggs that aren't green and are soft not rubbery and easy to peel. But in reading the posts here - this can all be accomplished a lot cheaper with a steamer basket and a timer.