I saw the film last week and was going to write something on it, but Ashok Malik says everything I wanted to in today's Indian Express, and he puts it in a much better way than I possibly could.
"Mangal Pandey is eminently watchable. True, it is not short of anomalies and anachronisms — Barrackpore looks beautiful, but is not usually overlooked by the Sahyadris; Lord Canning refers to the white man’s burden a half-century before Kipling coined the phrase; the real Mangal Pandey almost certainly never met Azimullah Khan and Tatya Tope.
Nevertheless, as a mix of history, folk tradition, legend and cinematic licence, the film is worth the price of the ticket. It is visually extremely rich, some of the sets are straight out of Company-era watercolours.
The drama and vibrancy of mid-19th century India is well brought out — snakes and painted elephants, glass bangles and throbbing music. Some of these are cliches, of course, to appeal to the overseas viewer, but in much the same manner as Indian novelists now seem to write only for literary agents in London."
As someone once said, read the whole thing (link).