Ok, regret is a strong word. Ain’t no learning like real life experience, right? But it does feel icky to buy stuff that doesn't work and thereby add to environmental waste (we try to donate or repurpose if paw-sible, but some stuff is not amenable to either). Now, keeping in mind that cats are the consummate individuals, I've only included products with a design or fundamental execution flaw. I have no affiliations with or ill feelings towards any of these products. However, as a type A cat parent, I feel a responsibility to share candid reviews.