Where I live in Michigan our summers are typically in the 80's and the winters can be 6 months of 0 - 40F. As such the forced air heating is on for at least half the year and this means that we have to humidify our shops in an effort to provide a stable environment for wooden instrument making.
I try to keep my shop in the 42 - 48% RH range and I don't worry much if it approaches 50%.
Over the years I have tried many humidifiers and in all honesty they all have sucked big time. They are either not powerful enough, noisy, smelly or the filters don't last very long. If you can clean the filters that is a real drag to have to do too....
The best humidifier that I had found until recently was a Beamis but it had filters that need to be cleaned every 5-7 days.
My water has a lot of iron in it here in the Michigan prairie and it also contains tanons which can cause the sulfur-like smell that you may have experienced when turning on a tap. So when I moved in I spent over 3K to have a 3 stage water purification, softener system put it and that system works great and my water is very clean, does not stink... and tastes great too.
The Air-O Swiss humidifiers are very high-tech and do not use filters that have to be cleaned or replaced. Instead the water is filtered through a demineralization cartridge prior to entering the working part of the humidifier. The humidifier uses ionic silver to kill bacteria and contains a replaceable ionic silver stick that lasts a year and requires no servicing.
This unit also preheats the water to a temp of 195F also killing germs and uses the juice of a 40 watt bulb. The unit uses ultrasonic sound to excite the water molecules which again is heated to 195F and then it exhausts the humidity through a series of duct work which cools the mist to a very pleasant 105F.
You can see the unit humidifying the air as the mist comes out which is kind of cool when you are used to wondering if your moldy old filter based unit is even working.... And my shop hosts visitors several times a week and in the age of swine flu Heshie here appreciates devices that automatically kill germs.
It's completely automatic with a built in hygrometer that tells you what the RH is and surprisingly this hygrometer is not too far off from my calibrated lab quality hygrometer. You set the level that you desire and set the speed (low, medium, and high are available) and the damn thing just works.
It's also completely silent. Hell - I like this thing so much I may even marry it...

Other than adding water to the removable tank with a great handle and design so it sits fine in a sink it's all very easy to operate.
Needless to say I am new to this technology so I'll be looking to see how it does over time and let folks know if interested. Air-O-Swiss also comes with a 3 year warranty which is way better than the competition and they make units that are bigger and smaller than this one.
When I factored in how much I spend every winter replacing humidifier filters when they just won't come clean anymore (north of $80) the $200 price tag, convenience, completely automatic and accurate operation, germ killing, and NO stinking filters I thought that it was a good deal.
Here are some pics - you may be able to see the mist coming out of it. Maybe it's time for a feature length motion picture called "Luthiers In The Mist"



