I've used these for nearly two years now, and they are the only boxes I use. I love mine and several friends have also purchased them after seeing mine. I have three cats, one of whom has renal failure so he pees a ton, and another cat with diabetes that isn't regulated so the boxes get heavy use. One of my cats has anemia and eats clay litter if his levels get too low, so I'm really grateful they exist. I have gotten urine samples from them but mostly they are just a nice system. I do not notice an odor with the boxes, but I clean them out regularly. I probably change seeds every 6 weeks or so, but remember I have two cats that flood the boxes. If seeds get soaked they will look gray. I scoop out solids and stir up seeds, then lightly mist with Clorox Everywhere. Usually the gray seeds dry out but if I start to notice any odor then it means that the underpart needs a quick clean or that the seeds need changing entirely. After about 3-4 weeks of use if you remove the top slotted tray you may notice that some smaller seeds have fallen through to the next level so removing them and using some Clorox to disinfect gives me several more weeks of use before seeds must be changed. When seeds are mushy looking I remove the seeds and dump outside (good ground cover and they do sprout) and disinfect the entire thing, including putting in new seeds. My friend has tried buying seeds at Lowes but I just buy their seeds because I have to change them so in frequently.
I am not sure if many people use them or not but I love mine! No dust, no heavy litter to buy, and no smell to deal with. Ive used pine, wheat, and corn litters and even one with rocks years ago, but this system is the best in my book.