I had a Short Tailed Opossum for about 6 months before we moved. In short, he was not as tame/calm as I had hoped, and much stinkier. Pare that with a more complicated diet and I will take a rat or a Virginia Opossum any day.
They are not pets that will bond to you IMO, regardless of what people say because of their solitary lifestyle in the wild.
Besides, STOs have the same life span as a rat.