I only have one at the moment and my cats fight over it! I had to cut down the pad inside so it would fit on my quite narrow windowsill but it works fine and they love it. Roll on payday when I can get one for every window!
I am buying another because my cats love it, but beware it does mark the paint on your window sill. The little raised points in the reverse of the mat leave mark in the paint that I cannot remove.
However my cats are happy with the mats so it's a small price to pay, unless you are impossibly houseproud!
My 4yr old cat loves this, often falling asleep when not watching the world go by. I have 2, one for each end of the window ledge so they do not move around. The black backing does leave small black dot marks on my white ledges but who cares, it's a comfy warm place for my cat and has been a real hit. Will be getting more. Just have to remember to take them off at night if you get condensation on your windows.
I tend to think of my window sills as fairly wide, but in searching for a bed to put on one of them, I struggled to find something that would actually fit without requiring screws or other fixings. (I live in a council bungalow so "permanent" stuff is usually a no-no.) This mat is the same width as my window sill and non-slip enough that it doesn't move around as a plain old cushion would (though it did start out in the centre of the window and slowly get pushed all the way to the left when KitKat walked over and around it. I do think it needs to butt against one wall to make sure it's truly non-slip). KitKat kips on it about half of her window time, so it's not perfect. I wanted it to keep her warmer when she's watching birds, but she'd rather sit on the other end of the sill while she does that, and only uses the mat when she's having a nap (facing me so I know when she's actually sleeping on it). Still, she seems comfy on it, and she can stretch full length on it if she wants. It's definitely worth £3.99, but I'm not sure it would be worth much more than that given how little of her day she actually spends on it.
This looks nice and feels nice however the backing on it has ruined the paint on my window ledge (white paint). It has left black dots (the backing is a dotted texture) in the paint which I tried to wipe off w/out taking paint off with no luck :( My thought is obviously the sun did this so if you buy this put it in a window that gets no sun which then defeats the purpose cause cats love sunshine! I give it 4 because it does look nice and my cats love it. I just have to repaint!