Very expensive.

If you have $200 to blow, and like the design, you buy a Venta.

Inside the Venta air cleaner is a water tank with a plastic revolving water wheel, and a fan that blows air onto the water wheel. The water wheel is about 8in long and consists of a series of 6in diameter disks spaced about 1/4 in apart. The water wheel is half submerged in the water. As it rotates it picks up some water and catches some dust and deposits it into the water tank. The fan and water wheel increase evaporation. It has multiple speeds.   It would be nice if you could disassemble the water wheel, but as it is it is fairly easy to clean.

The fan motor is housed in a way that it is very easy to remove and clean. This is the only household device that I have found that made removing the motor, which gets covered with dust, easy. I would say this is the most impressive feature.

The fan is quiet but not silent. At 10 ft from me I do hear a dull drown. I am surprised they do not advertise it as one of those static noise machines that help you sleep. If the radio or TV is on, I do not hear it. In general Venta looks and sounds like a desk top computer.

The power cord is about 5 ft and should be at least twice that given the price of the thing.

They should be designed so they are stackable if you own more than one.

You cannot see the water level in the Venta, so a forgetful person might not notice it is empty. Venta should either have a transparent tank or a buzzer that goes off if it runs out of water.  It might also be nice if you could run a hose and fill it automatically. 

The most annoying feature is you are expected to add Venta Airwasher fluid to the water. The Venta Airwasher bottle does not have the ingredients on it which I consider to be irresponsible, especially around children. Buried in the manual:

Water blend Quarternary Ammonium Chloride and water softening agent. Quarternary Ammonium Chloride may be dangerous, or maybe not. They need to discuss this in the manual and their advertising. This is the only thing I was able to find on the subject. The machine works without the fluid, using just tap water.

"Since the pH of blood is slightly basic, the presence of quaternary amines in the body can be potentially dangerous."

DETERGENT ENZYMES
How safe are they?

http://www.ecogent.ca/enviro/env_enzyme.htm

I may sound alarmist, but the kind of person that pays $200 for 'good design' is the kind of person that resents putting unknown and unexplained chemicals in their environment. They really should give a recipe for home made fluid after all I did pay $200 for it. I find dish soap and ammonia or vinegar added to the water works fine.

It does remove odors, especially if located near a smoker.  The fluid turns yellow over time.

If you are into it you can add aroma therapy fluids to it.

I do not use their fluid. Along with the recommended amount of water I put a dab (literally, very little) of dish soap, and a table spoon of ammonia or vinegar (you should not smell it) in it.

It DOES WORK:  After a year I can say it does work (it puts about a quart of water into the air each day) and it does clean the air (If I let the water evaporate there is a yellow residue from smoke).

UPDATE: I am seeing the 2 gallon ones for sale at $100-$150.  So I think that is an ok price.  I still think they should suggest how to mix your own cleaning fluid.

You may not be able use it in the summer as an air cleaner as it will humidify your home making it very uncomfortable.  Depends on where you live. 

Spare Parts:  Checking out their web site they do sell most of the parts incase you break something.  Unfortuneately they do no sell the upper part of the housing.  That part has many doors and flaps that can break.  So while I like the fact that they sell some replacement parts, I cannot give them full marks until I can replace all the parts.