We tried this with my Simon kitty (who died last June), but I wouldn't do it again with a cat. Simon adapted to it right away and was always curious to explore when we got him outside. Simon loved it too much - it made him all the more determined to get outside, and he got too comfortable being out there, so when he escaped he would wander farther. Our current cats, Beatrice and Rosalind, are strictly indoor only cats. They both try to get out, but when they do manage to escape they stay close to the house.
There are also "cat play yards" that are designed for your cat to play outside without being on a leash. Our friends have one of these that they got online. They let their cats out into the "play yard" a couple times a day and the cats eat the grass and nap and play there. I think it's funny!