The most common tranny problem discussed is throwing the differential pin, which applies to both auto and manual. The pin doesn't hold up well to sudden jolts, such as spinning tires that suddenly make traction (doing burnouts, spinning tires on ice and suddenly finding dry pavement, etc). Throwing the pin pretty much ends the tranny - could grind the internals, could punch a hole in the housing.
I'm not familiar with any other terribly common saturn tranny problems. Mine works fine so far.
