they work very well. nowdays they have a replaceable screen that you replace once a year that takes care of calcification problems.
http://www.nextag.com/honeywell-whole-house-humidifier/compare-html

I would imagine they are pretty much mandatory these days, so yes indeed they work.

They do require some maintenance, but, by the same token, so do furnaces.

The Desert Spring rotary disk humidifier seems to be pretty popular, I plan to buy one at some point when my current one packs it in (usually there is a motor and a couple of moving parts in them) the are a little pricey but they don't use a foam pad so they are a little cleaner and don't require replacement parts as a matter of course.

Here is a link that might be useful: Desert Spring Rotary disk humidifier

Thanks pjb and vhehn! The Desert Spring looks like a very nice choice especially with the Auto flush self cleaning function. It seems to me the price of the unit is probably not the biggest thing compared to the cost of installation so you might as well pay those installation dollars for something that will keep working well over time. Funny. I'm a real estate broker and deal in estate type homes and I NEVER see whole house humidifiers in the basement. Maybe it's just that we are very rural here or because in second homes people just don't mess with it? I don't know. I guess I'll be a first.