I've used a hova-bator for a long time, but for chicks. You change the temperature by using a lever-type thing on top, and monitor with a thermometer inside. I suppose a thermostat would be really helpful, though. I've had my current one for about 5 years, and it works great for chicks, but I probably wouldn't use it for BP eggs. It does spike occasionally and does change with the temperature by a few degrees if it's close to a window, but it works well for chicks. If you do decide to use it, set it up at least a week beforehand to get the temps and humidity as correct as possible, and try to get the model with the fan, otherwise the heat sits at the top and the eggs stay a few degrees to cool.