I remember this summer 2007 just gone; we had the noble scholar of Kuwait Shaykh Falaah Isma'eel al-Mundakharee in Slough giving a lecture. In it he mentioned the statement of Umar al - Faarooq (radiAllahu anhu): "learn arabic, for verily it is from your religion" - showing and stressing the importance of learning the Arabic language. Having attended lessons of Madeenah Arabic Book 1, the teacher introduced the importance of learning Arabic and the general principle from Shaykh - ul - Islam Ibn Taiymiyyah (rahimahullah) that "the means to an obligation, is an obligation in itself" - just like worship of Allah alone is an obligation, then seeking knowledge is an obligation as worship is not correct, except with knowledge (which is the Quran and Sunnah upon the understanding of the Companions of Allah's Messenger (salAllahu alayhi wasallam)). Likewise, understanding the Quran and Sunnah is an obligation, therefore learning the Arabic language is an obligation.
Alhamdolillah I found the Madinah Arabic Books very beneficial, they are very simple to read and contain the beginner grammar rules to get you started. MashaAllah I know brothers who have self-taught the basics of Arabic language and a majority of them began with the Madinah books. So for brothers or sisters who have some exposition to reading Arabic from school or being able to read Quran (or even urdu), the beginner books are very legible. However, to understand grammar rules from the books, even those who give themselves a head start will tell you that having an experienced teacher is imperative for better understanding. The Madinah Books do not have overly detailed conversations in them and instead are aimed at aiding the learning of Arabic Grammar rulings to help read and understand the Quran and Hadeeth accurately rather than speaking. None the less they certainly help with speaking, but one should also invest in other Arabic books, like 'Gateway to Arabic' (various levels) by Dr. Imran Hamza Alawiye. So long as the dialect is fussha, as is the classical Arabic language of the Quran.
Finally, for someone who works and has family, I definitely recommend the Madinah books and that one strives to learn as much as possible, likewise the young and single, but the advantage for them is that they could go out to countries like Saudia Arabia or Yemen who teach these books as a Curriculum with a teacher wal hamdolillah.
Zahoor Yousaf, Slough, UK