I didn't have a great deal of success with mine, because the house we lived in at the time was old and draughty and they need to be somewhere where the room temperature is pretty constant - they just can't cope with even medium fluctuations.
If you have somewhere that is a steady temperature, then I think you get reasonable results, particularly if you rig up a computer fan to turn it from a still-air to a forced air machine. They are a good 'starter' to learn about it all.