While it is a type of exchanger the jury is still out about alot of things, including the insane effeciency numbers that have no real data to back them up. There is a definitive essay on DX on my website. @ weberwelldrilling.com
Please understand that I am a driller and it makes no differance to me at what angle we drill, or what we put in the hole, save for reliability and long term customer satisfaction. For me it is just not there with DX. I am paying close attention and will make a buck with them if they address their issues to my satisfaction.