Unfortunately, the exact reason finance people will like it is the exact reason it will have zero commercial appeal.
The 30-second recap: Margin Call takes place at a fictional bank in the early days of the financial crisis. The bank sees the writing on the wall, and its CEO John Tuld (Jeremy Irons) makes the decision to dump a ton of MBS onto the laps of customers, a move that may save the bank's balance sheet but potentially ruin its reputation among clients (not to mention ruin the reputation of traders who have to sweet talk clients into buying into the firesale).
The film explores the moral dimension of high finance: Sam Rogers (Spacey), the longtime head of the fixed-income trading floor, wrestles with the ethics of Tuld's move, and wonders whether he should've just gone into ditch-digging. An up-and-coming young risk analyst with a background in physics tries to believe that the whole thing is more than mere gambling.
It's all good stuff, and well-acted.