I use the combinations of Keens with Frogs, and I love it. I did have to carve a bit off the bottom to fit the cleat in. Any other spd type cleat should be fine too.

Personally, I don't like to wear them for rides over 40 miles, especially if they're going to be hilly miles. They are a bit more flexible compared to road shoes. However, many other TE'ers like them just fine for longer distances.