My husband says that hard boiled (we actually steam them) duck eggs are ten times better than our chicken eggs! I personally would not know, because he always manages to get them all eaten before I come along. But he says they are sweeter and more creamy.
As far as frying them up, my duck eggs remind me of the taste of store bought chicken eggs. I have used them to bake angel food cake, and they work great - fluff right up.
Overall, I prefer fresh chicken eggs myself, but duck eggs are good too.
The number of eggs they lay depends on the breed. My ducks lay on average about 300 eggs per year.