Product review (5 stars): These work great for me
These work great for me.  I have 1200 sq ft with 6 of my 11 floor vents using these humidifier registers.  I don't have dry skin or lips and no static anymore from dry heat.  I have very long hair, I sit on it when it is down, and static is a major problem when the air is dry.  Since I've been using these registers, I don't have static in my hair nor with clothes. My plants are also happy with the moisture from the air!

These do what they are meant to do, add moisture to the air. They do take a bit of work though. When first put in, the wick absorbs the water pretty quick so you have to add water right away. Since I work full time and I try to conserve energy, my thermostat is set low when I'm at work and when I sleep.  Otherwise, I keep my place between 68-70.  I've made adding water part of my routine and fill when I get up and when I go to bed normally.  When I'm running the heat more to keep at 68-70, I do have to add water more often, but I tend to keep it full rather than have it run out of water.  When that happens, the wick filter gets dry and has to do the absorb thing again.

I have a plant water container that I use to fill them and have no problems doing do.  There is plenty of opening to fill it and can see when the part that holds the water is full.  I also fill the max I can without it overflowing into the vent which seems to be more than 2 cups.

Yes, you have to pay attention to the water level and keep them full so it does take a bit of effort. But it's not hard and the few minutes a couple of times a day it takes me is well worth the results.