I started with walking, and then added walking poles. It's actually really effective, then the technique is right - when you really push yourself forward with the poles, like you were skiing. To my surprise, I have actually gained muscle in my arms because of this.
It's also considered a safe way to exercise, as the poles help you keep balance, and weight is taken away from the knees. Great for those who can't run for a reason or another.
From
http://nordicwalking.co.uk/:
Physical Benefits
Tones the upper and lower body at the same time
Uses 90% of the skeletal muscles
Burns up to 46% more calories than ordinary walking
Reduces the pressure on knees and joints
Great for the Heart and Lungs
Ideal for neck, shoulder and back problems
Poles propel the walker along, making it easier to move faster then normal without feeling the effort.
It is one of the most effective cross training techniques for athletes and sportspeople who require ultimate cardiovascular and endurance conditioning.