Do you know of any current research on the calorie expenditure when doing Nordic Walking versus regular walking?

Yes, there is. The Cooper Institute has made comparisons and found that walking with nordic poles increases energy consumption by about 20 %. Check out the entire article by following this link http://walking.about.com/cs/poles/a/polestudy00_2.html .

I am German and had noticed how many people use them in Germany as part of their exercise program. So I searched the German language part in google and found many web sites that provide good information. You can put in the search words "Gehen mit Stoecken". All of the sites can be translated with the automated translation software. And while those results are linguistically rather pitiful, you will still get an idea of what they are trying to say. At the web site www.bergnews.com is good information about techniques in mountainous terrains and the advantages of using poles there.