Our Golden Cuckoo Marans consistently lay dark eggs, way darker than our other breeds, however, they do vary between dark eggs to very dark eggs. To me, they didn't start laying early, nor are they extremely great layers.
Our Appenzellar Spitzauben's lay fantastically. About once every day for each hen. However, it took FOREVER for them to start laying. Several months after our last breed started laying so that I definitely a con. But they have, I think, made up for it by being so reliable.