Just finished my first "test run" hatch. I turned eggs twice daily before setting and used an electric turner in the incubator.
On Day 18 I candled and had 12 viable eggs. I put 6 under a broody hen and kept 6 in the incubator. Only three hatched--days 20, 21, and 22 (another one had pipped and quit on day 19--pip was in the center far from the air sac). I did have a high humidity issue on Day 18 but got it back to normal pretty quickly. I had put water in all the channels, not just the center and second ones.
Is that a poor hatch? Average? The broody didn't hatch any of hers, so I don't know if it was the eggs or if she got off the nest too long or something else. 
I'm ready to try a full tray of 42 eggs on Wednesday.