I saw it the night it premiered on HBO. The night before that I also saw "Inside Job" (
http://www.sonyclassics.com/insidejob/) so I felt both together did an OK job of explaining the crisis to the lay person.
My own personal take, with tons of bias, comes next. I personally felt that "Too Big To Fail" was a little too sympathetic to Henry Paulson and Ben Bernanke. That could be because the actors who played them were both so fantastic and try to approach their parts from their characters point of view, that the actors themselves came off as sympathetic. I felt that the film glossed over the parts that Paulson and Bernake had played in setting up the background for why this crisis came to be. If anything, I think it leaned a little too right.
On the other hand, "Inside Job" I felt leaned a little too left. I wasn't really impressed with Barney Frank being the voice of one of the good guys, when he repeatedly insisted prior to the collapse that Fannie Mae and Freddie Mac were in good shape, when they most certainly were not. Other than that though, Inside Job was better in showing the lead up to the crisis.
Definitely see if it you have a chance... even better, watch both.
I think there's too much pointing left and pointing right. My take, both sides failed us politically.
As far as the OP's question
If that's true should we be concerned about letting banks hold our money or should we start using cash only?
My own personal choice was neither. After all this happened, we moved to a credit union.