Yes, I'm a cat owner and I bought this to find where they'd been secretly 'marking'. The little beggars had been driving me crazy, no matter hiow hard I cleaned, I could still smell it. Rather than go insane, I bought this.
It finds all the tiny little places you missed, for a start and that makes a real difference. It does work for finding urine, but some surfaces work much better than others. eg a harder surface is perfect for it, whereas it's less effective on softer areas. Also, it does have to be good and dark to show you everything, especially on lighter material.
The reason I gave it 4 stars instead of 5 is that battery life hasn't been great and also, it finds wallpaper paste too...which did make life difficult as I was manically scrubbing the walls before I realised!
Definitely worth buying.