I got the NuFace Mini a couple of years ago, and didn't see great results - but to be honest I found it a total faff to use and didn't keep up with it consistently.
I didn't have time to use it in the mornings, so I tried using it in the evenings. I had to wash my face first (even if I wasn't wearing make up, I would have to remove traces of sunscreen), put on the sticky gel, which I hated the feel of, use it on each side of my face for 5 -10 mins (I couldn't really concentrate on watching tv or anything during this, it was too distracting).
Then I'd have to double cleanse to get the gel off, before I could put my actual skincare on. Also, sometimes I would get little flickers of light in my eyes when using it, which freaked me out.
I'm quite lazy, so it didn't suit me at all. If you're going to invest it in, be sure that you will put the time and effort for it, I didn't.
I know some people claim it's brilliant, but I remember seeing dermatologist talk about it on youtube, and they said there wasn't much research behind the technology, so I'm not sure.