I have three: Marsh RollX, Hovabator and a Jamesway (very old, no literature available for it).
The RollX and the Hovabator are used most. Eggs are transferred from the RollX at 18 days to the Hovabator, it is an excellent hatcher. I agree with the one of the others, that sanitation is an issue with styrofoam incubators, so they have to be thoroughly cleaned after each hatch. I use common bleach. Hatches are very high 90-95%. Sometimes 100%!!! The Hovabator keeps temperature pretty well and to get the humidity up I put thin sponges under the 1/4" wire, taking care not to cover the air holes and soak them when eggs are put in for hatching. Both RollX and Hovabator are excellent for beginners.
NOTE: See "Jamesway" for comments on that brand. RollX and Hova bator comments are the same under both links.