Walking is a great activity, and it is wonderful that you have established a healthy routine. Getting out there and moving is half the battle! You are burning calories during that hour or so of walking and improving circulation and exercising your heart. That's great!
That said ... the faster you go, the farther you will go in that same time period, so the more calories you burn. Walking faster will push your heart rate up higher, so will work your heart harder, and build your aerobic capacity and endurance. It depends on your goals. If you want to improve those things, then one way is to throw some "power walking" intervals into your walk, or even a minute of jogging, if you can. That will increase the intensity and benefit of your walking time.
Just my thoughts!