Leonardo Davinci was ambidextrous. He was a Polymath which means he had attained world class knowledge and skill in a number of different areas. He is considered by many to be the smartest man who ever lived. He was creative, hyper intelligent, physically very strong(He was said to be able to bend horse shoes with his hands.)a brilliant artist and painter, a musician and composer, an engineer and the list goes on. He was the best in any field he endeavored in for the most part.
In fact, I can think of only positives. This skill could improve tasks and hobbies such as handwriting, piano playing (as noted by the picture), and there are countless numbers of sports that depend on hand usage, and a player's skill in these would be improved by an increased talent of use in both hands.