As others have said, it is good when it works But, as they have also said,, it doesn't work or stay working for long.
My first one I bought at full price at Target. It worked the first time, but then I put it away and it failed the second time, maybe around warranty's end (had already lost the receipt). However, I did do use reverse osmosis water in it (which the instructions implied would be OK), and it had had a few gentle knocks (but nothing severe), so I chalked it up to that. Although I still felt it was much more fragile than it ought to be for the cost,, I managed to find another corded unit at Target eventually; this time it was (apparently) just before the release of the cordless version, so it was slightly (but not much) cheaper; maybe $129 instead of $149still expensive. That unit worked first time and also stopped working the second time, but eventually revived by letting it sit around filled for a few days. I only used store-bought distilled water in this one, Fast forward a couple of years and I've used it occasionally and it is admittedly still OK, but for me it still doesnt' help as much as a hot shower or as much as I'd like for the cost. I decide I like the cordless one, but don't want to risk/shell out another $150, between my experience and reading pretty much on-line in many places that the fragility hasn't improved much. So I found one new in box on ebay. It was DOA, and it did appear to be unused when I got it. Service initially said they'd fix it but when they found out I got it on e-bay, it was not an authorized dealer, so they refused. They suggested it might be old or counterfeit. Old? The product's only been out less than or around the two years they now want to warranty you! Counterfeit? OK, I'm willing to send them back the unit to inspect (not that I'd necessarily trust them, but that's reasonable to ask). I had given them the serial, and I subsequently got the date and place of original purchase from the seller (which was the current year, 2019, at Walgreen's, which was an authorized dealer), although not the receipt. That should have been enough for them to at least consider it might be legitimate, but I feel they just wanted an excuse to not stand behind a product which has a proven record of poor design and frequent failure. They suggested I ask for a full refund from the seller (not reasonable; the seller had fulfilled their part of the deal) and they would give me a "discount" on a new one. I decided not to send good money after bad.
Incidentally, although it is helpful, it isn't as good as a hot shower for me, so its utility even at best is marginal for me, hence my further reluctance to spend more $. Maybe this one will fix itself too (although it doesn't seem to behoping they might release a new firmware version and updating it will reset things, but who knows). YMMV.
Caveat Emptor!

My puremist replaced it. Same problem again. The unit is not compatible with other distilled water.