I have the Eco 20 with the automatic turner, and I LOVE it. I had 16 of 17 eggs hatch in my first batch, and have 15 eggs in there now (due to hatch this weekend!). I have 2 themostat/hygrometers in it to monitor the temperature and humidity, and only have to add water once in a while to keep the humidity where it needs to be. I think it would be too crowded to hatch 24 chicks, but for the 16 I hatched it did just fine, and was really easy to clean.
I will eventually get a hovabator, or a cabinet incubator for hatching since they have more room for the hatching chicks, but since I'm not hatching out more than a few at a time it works just fine for me.