Built my own with a large cooler, heat cable and a good thermostat. Temp fluctuation is only half a degree Fahrenheit which I think is great.
One of the guys I know had a reptibator and he said the temp fluctuation was ridiculous and when you take the lid off it takes an insane amount of time to heat back to your ideal temp so he never used it after his test.
Don't know much about the others except the Temp readings can be way off on the "all in one" incubators but as long as it's monitored with good equipment I can't see that being a problem at all