I used Michel Thomas for Spanish and have done so again for Portuguese. However, with Michel Thomas, it is excellent for learning the structure of the language but it should then be combined with a book of some sort, e.g. Hugo in 3 Months (which is a book and CD based course.). I have just done Michel Thomas beginners and advanced, and am now using a Portuguese Verbs book. Plus of course my girlfriend is Brazilian so I am using the book then she goes over pronunciation and helps me practice.
With Michael Thomas he teaches the Spanish in quite a heavy German accent. In Portuguese, they use the same structure but have a Portuguese speaker repeat every phrase so you learn it properly (although Brazilian can be different in places).