How do you clean it between different oils?
Rinse then let it soak in warm water for 10 minutes. Afterwards I dump the water and wipe it with a cotton tip.
What is the voltage on the plug-in adapter? Is it 110 - 220 or US-voltage only?
It works on 110v to 240v. The unit itself is 12VDC, but the power adaptor can take 110v to 240v. The plug is the US plug but you can find an adaptor for another country.
Is it quiet?
It is very quiet. I had a different brand that used to wake me up when it was running out of water. This one does not do that at all.
Can light be off completely while misting?
Yes. The aroma diffuser comes with a remote which has a function to adjust light color, brightness and light-off (while the aromatherapy diffuser is still running).
Are there any reviews out there from people who DIDN'T receive this product for testing/reviewing purposes?
I purchased this product to use in the bedroom and then bring to the hospital when I give birth. So far it works well. It runs for a long time, turning off the mist periodically on it's own which I like so it seems to stay on longer. Remove the lid delicately so as not to make a mess as I have done a couple of times because I thought it should be out of water by now. I was wrong both times. It seems to shut off entirely, light and all, once it runs out of water. I am happy with this product.
Why can you only use aromatherapy grade essential oil and not therapeutic grade?
Typically aromatherapy grade essential oil doesn't have any fillers and that it has a higher grade content where it is easier to mist compared to therapeutic grade essential oil. We only approve usage of aromatherapy grade essential oil because if using other types of oil, the chances of gunking up the ultrasonic plate is much higher and thus easier to damage the unit. So from both an essential oil perspective and warranty perspective, we only recommend aromatherapy grade essential oil.