Though I am predominately right-handed, I have trained myself to write with my left-hand. Granted, it's not perfect, but I would say my left-handed writing ability is above average, considering no one seems to inquire this (as if this were visibly noticeable), and I write left-handed on a regular basis while retaining my ability to write with my right-hand.

As for everything else, I can use both hands just fine.