I've one for cleaning hard and vinyl floors and it is very good, better than a mop. A containerful of water lasts for several washes, as it just heats it as it passes through to the mop bit, and the rest stays clean. You can plug it in, give it half a minute to heat up, then wash the floor (a quick once-over with just water or a more thorough one with detergent sprayed on the floor first) The corner where you started is dry before you reach the far corner, no keeping out of the kitchen while it is still wet. When the mop gets dirty, the cover can be detached and thrown in the washing machine.
It also "refreshes" carpets - ie you can clean a spill or a spot, but it is not as thorough as a proper carpet cleaner. Fine for footprints when someone comes in with dirty shoes.
Mine is a small Vax. It doesn't do upholstery or windows. Some do. I bought it greatly reduced because it was a reconditioned "returned or with cosmetic faults" one. I'd have said that it was new, and it had a year's guarantee.