We didn't have luck with ours. 1 egg made it to what looked to be full term, but the york was never absorbed, and it never hatched. another egg just started to form, and stopped. The other was non-fertile... and the 4th egg had a formed chick but s/he was deformed. Looked way off.
Next year we'll be getting a new bator, so hopefully we'll have more luck. This was a "just for fun" run.... however we found our missing hen with 10 chicks in tow...so it all works out