The only major downside I experienced with being left handed is the smearing of ink or pencil lead every time I try to write something. When using a lead pencil, this smearing is called "Silver Surfer Syndrome".
When I was in school & used erasable ink pens,the side of my hand would be smeared with ink & my paper would be a mess. I had to use another piece of paper, under my writing hand, as I went down the page to prevent smearing.
It was extremely annoying, & one of the reasons I prefer making art or writing on the computer. In college, all the computers in the lab had the mouse on the right side.
Therefore, I just ended up learning to use my right hand for the computer mouse. As a professional designer, I still use my right hand with the mouse! So, I guess I'm actually ambidextrous!