Your question is whether this movie is useful in introducing Indian culture to viewers.  The answer is yes, of course.  No matter if it's totally accurate or totally inaccurate, the film is a way of starting a dialogue about what is real.  That's the benefit of all the arts--they provide an opportunity to talk about views and perspectives and issues and ideas. 

I think the film has many redeeming qualities as a work of art and a study of characterizations.  Certainly, the characters of Jamal, Latika, and Salim (even Prem, the host of the show, and the police interrogator) are very fascinating and possess a sense of depth and dynamic natures.  Additionally, I think the film tells a fascinating story and the interposition between the questions and the personalized narrative is also intriguing.  There should be an inherent danger to taking any sample of popular art as a "cultural sample."  Certainly there are some elements within it which are valid and there are some elements that are not.  We can credit the latter to some level of poetic license.

However, where the film is valid is in its assertion that societies have an inclination to use economic status as a measurement of character.  We hear the refrain often in the flim: "I must have cheated because I am a slumdog, right?" Exaggerated as it may be, societies do have a tendency to discredit and disparage those on the lower end of the economic scale.  In many profit driven social settings, wealth and the acquisition of it, subconsciously transfers the impression that wealth means better.  It is present in all levels of all societies, and this is due in part, to the emphasis of materialism in capitalist societies.  In these settings,  wealth is not merely an extension of a person's work, but is actually a mistaken impression of their character and worth.  We try to avoid this, but social orders are predicated upon this.  I think this element is brought out in this film and reflects elements of Indian society, as well as many others.  Class and socio- economic status is one of the hurdles that has proven to be challenging to overcome for quite a long time.