Have any of you used the various cold air gun coolant
systems and if you have, what are your opinions on the
products?

http://www.exair.com/spotcooling_products/cg_page.htm
http://www.airtxinternational.com/ca...FUgxIgodaXyN-A
http://www.pelmareng.com/Spot_Cooling_Systems.html
http://www.4-airknives.com/cooltool.htm