Ours love it and even the 18 and 20 year old still get up on the window sill every day to have a few chews of it. And yes, they still can get up on the windowsill.
We used to dig up a small chunk of lawn each Fall and that worked too. Then we grew our own cat grass, from grass seed and oats. Now we just buy a pot in the grocery store for usually around $2.00, much easier. We'll need 2 or 3 pots to get through winter.