I'm on the Nay side.

Rainbow has been around for how many decades? It's not sold in stores that I've seen, it's sold door-to-door with pushy salesmen and rigged demos.
I mean, let's face it, there's nothing revelatory about lint and dust in your carpet - or shouldn't be.

And I don't even know that there's a knockoff out there. Is there? Even Hoover and Kirby - also once sold door-to-door - has plenty of knockoffs and competition as soon as their 17 year patent protection expired decades back. Yet even now, Rainbow does not.

See, when it came to my house, 25 years ago, I just saw "a fan and a puddle". The water is the "filtration" and the fan is, well, a motor that forces ambient air past the boundary layer. This didn't keep Wernher Von Braun up at night. Total price? A fair one shoulda been about $60, but this guy wanted something like $800 (my wife just said). I just couldn't see the value. I don't think the used market does, either.

It works. I'm sure it works. What's NOT to work? I'm sure it works in the long term - despite running what's basically a table-saw motor continuously. But I'm equally certain it gobbles up the kilowatts for a somewhat limited solution to an even less diabolical problem (than the salesman would have me believe). After all, i should've died TWICE by now of respiratory malady, according to their pitch. Worse, I've never lived in any house that was sealed so well that at least that much dust couldn't enter daily from leaks -- or be introduced from opening the door once or twice.

If a guy has one, well, good for you. Here's to your loving it and keeping it. Not saying you're wrong; made a poor decision; or were gypped. Just not for me. I don't know what I'm missing. The idea, and the execution, just never really blew my skirt up.