I listened to many of the CDs using the Michel Thomas method for Italian. I really enjoyed the method and learnt a lot from it. I would not say that his accent is close to a native Italian accent; however his pronunciation is very good. That is, he does not make many errors at all in important Italian pronunciation points (e.g. double consonants, the vowel sounds are distinguishable, etc). However, his accent sounds like native German to me when he speaks English, Italian and French.
When Michel Thomas passed away, some other materials were made in Italian that involved an American woman teaching. I find it awful to listen to, as her American accent is incredibly strong when speaking Italian and she makes very obvious and important errors in pronunciation, often!
I've also seen other reviewers comment on this. They do use a native Italian speaker in these CDs (after the pause when the listener practises the word); however the woman is the one teaching and the main one to speak Italian.
She has the last word, so it sounds like she is correcting the pronunciation of the native speaker (e.g. "Very good: (her pronunciation)". Having said that, the method is so good I still learnt a lot from listening to those CDs!