The humidity motor is not necessary either, if you are willing to fill the water channels in the bottom of the incubator every day. This is easily done with a piece of aquarium tubing through the vent or by lifting out the egg tray (very easily done).
The hard plastic is easier to clean and disinfect than the styrofoam units. If you end up with strofoam, you might want to line it with a oven roaster bag or something to make clean-up easier after hatching.
The hard plastic is much harder to break than styrofoam.
The thermostat and fan have kept mine spot on once the desired range is found.
The only disadvantage I have noticed is the small size does not leave a lot of room for hatched chicks to get away from still hatching chicks. So when the incubator is full at hatching, it gets pretty crowded in there, lots of egg-football.
I have been tempted to get a second one just to be able to spread them out for hatching. In such a case, I would only need one turner, as no turning is needed during hatching.
There is not quite the visibility of the eggs that other units with larger windows have. So you may not get to se an egg actually hatch if the ones in the middle hatch first and the hatched chicks kick the unhatched ones to the center as they move towards the outside windows to get a look at you trying to get a look at them!
Mine always seem to hatch at night, so I have yet to see one actually hatch anyway!