Hi, I'm a native spanish speaker and from my point of view Michel Thomas Spanish course is excellent;All I can say it's just excellent;Very recomended.
I was searching some reviews on Michel Thomas German Course and ended up in this website, so I downloaded the fist three lessons of Michel Thomas Spanish course, and was so funny to listen him speaking spanish (he does speaks spanish like a native speaker).
So,now with reviews I founded in this website and from my own experience with Mr Thomas Spanish course,I have no doubt I'm learning from the best teacher.
Again,VERY RECOMMENDED!