We've got a
Rainbow E-2.
Was it overpriced? You bet.
Is it the absolute best vacuum we've ever used? Yep.
Will it last for 20+ years? My parents have a friend that have used one for longer than I've been alive (29 yrs).
Pros:
No bags or dusty canisters to empty. It uses water to capture all the dust and dirt (fine ash [not water soluble] is filtered out by a HEPA filter) so the air coming out of the exhaust is actually cleaner than when it goes in. It'll actually take the smell of bacon, fish, etc. out of the air just by vacuuming our house or letting it run in air filter mode (low power).
It will also suck up water with no issues and it too "never loses suction" [that's an outright lie for any vacuum though. At some point the canisters will become too filled to hold any dirt and will then clog the intake. It takes more dirt than I'm sure your carpet is holding but it
could happen]).
It's extremely well made. Heavy plastic housings with heavy rubber bumpers and stainless steel attachments.
The beater bar is crazy easy to take off and clean with no tools. An extra belt is included and stored in the housing should the attached thick one break (pretty unlikely).
When started it sounds like a turbo charger spooling up a jet engine. Useless? Yes, but I do love that sound.
Cons:
It's a two part system. The beater bar is separate from the canister/main vacuum so it's harder than I'd like to lug around.
It's heavy.
It's a pain to clean until you get it down. The canister has to be dumped out then rinsed out. The separator (separates the air from the water) has to be unscrewed (tool included in the housing) and cleaned as well. Then everything has to be dried.