The nation's too-big-to-fail banks have now reported earnings for the three months ended Sept. 30. It was a rough quarter, to put it mildly, with revenue falling at all of the nation's biggest banks compared to the same period last year -- with the exception, that is, of Wells Fargo (NYSE:WFC).

As the results rolled out, a number of important story lines emerged, touching on the operations of JPMorgan Chase (NYSE:JPM), Bank of America (NYSE:BAC), Wells Fargo, and Goldman Sachs (NYSE:GS), among others. Generally speaking, Wells Fargo reaffirmed its position atop the banking industry, JPMorgan Chase and Goldman Sachs turned in atypically downbeat performances, and Bank of America proved for a second quarter in a row that it may have finally put the financial crisis firmly in the rearview mirror.

For a brief overview of four things that caught my eye in particular last quarter, scroll through the brief slideshow below, which covers the most important takeaways for investors in JPMorgan Chase, Bank of America, Wells Fargo, and Goldman Sachs.