One of the people I've talked to was the owner of my LFS. He said that he would maintain the little sensor thingy religiously, and it still kept overflowing the tank. He also said that he had tried different kinds, from DIY to expensive set ups, and he never had any luck with them. Another person I spoke to said that after the 3rd time having water all over the floor, she got rid of hers and went to adding water manually. To be honest, no one that I've talked to them about in person has liked them, but I have read a lot of threads and such where people have had great success with them.