Alex Chilton, Jody Stephens (drummer) from the original band have been playing with Ken Stringfellow and Jon Auer of the Posies as the reformed Big Star. They've put out a 1993 Live album and In Space (2005), but neither lives up to Big Star in its prime (nor does Alex Chilton's solo stuff).
They are the godfathers of powerpop. Badfinger is a good comparison, but there's a quirkier, darkness with Big Star (even if two guys from Badfinger committed suicide). Todd Rundgren and The Nazz are also comparable. But Big Star is the best for my money.
Chilton was into Marc Bolan and still does "Jeepster" and some Kinks' covers. Chris Bell was gay and tormented in the closet. He was also a pretty serious addict. Their stuff was recorded at Ardent Sound in Memphis (where Led Zep and The Replacements recorded).
The movie is based on a book by Rob Jovanovic (think that's his name). I'm wondering if the movie producers are shopping around for some money. That's the last I heard.