The core problem with Mangal Pandey is that it is neither an authentic rendition of true historical events (a la Ajay Devgan starrer Bhagat Singh) nor is it a tale of the triumph of the human spirit against all odds (a la Aamirs own earlier Lagaan). The film falls between these two stools and leaves the audience with a feeling of unfulfillment.
Human beings like to place each new person/place/movie/event they encounter into a familiar slot, much like a matching process. My guess is the audience hasnt been able to do that with this film. (True, they didnt do the same for many weeks with Sholay years back, but thats another story :) )
Will Mangal Pandey pick up in the next few days, after people have forgotten the initial disappointment? Will people forgive the huge hype created by the movies marketing team and value the film for what it is, rather than what they expected it to be? Will the remedial promotions undertaken by the movies marketers succeed in drawing the disenchanted crowds back into the theatre seats?
Only time will tell. But I reckon not likely.
Epilogue: My favourite piece from the movies pre-launch hype was when someone said the film received a standing ovation at the Locarno festival. Well, in civilised societies, people stand up and applaud a piece of art out of sheer courtesy and decency!