I just got one of these to use in my office last week. I've been testing it out over the weekend and it has been working quite well for me. One thing that I will mention: The adapters that come with this unit do not fit on standard American 20oz bottles. They are sized for a european sized opening. The instructions mention Evian and some other brand of bottled water that has this size opening. I had to go pick up a couple bottles of Evian to use. I'm sorta surprised that no one else mentioned this.
Otherwise it's been working with for me for several days running for extended periods.
2012-01-28 Addendum: I've now had this for some time, and it's still working well, although I've found my office is apparently connected to the desert, and I've had to move up to a larger humidifier. Also, an additional note on the adapters. I re-checked my adapters after reading in some reviews that people got this working with US bottles. Upon close inspection, the 3rd adapter IS slightly smaller then the other 2. I think it's intended to be sized for the plastic screw top opening common to US products. That said, I had tried all the adapters when I got it, and I re-tried just now to be sure. I think the adapter I got is either bad, or it's not made with tight tolerances. I am unable to get it to screw all the way onto a bottle, it almost always cross-threads. When it doesn't, it won't screw down very far, and as a result, water leaks from around the adapter, so it's un-usable for me. Maybe I just got a bad adapter there, your mileage may vary.