I have not gamed for a long time and was never very good at it. But back when I was gaming 10 years ago, I used trackballs exclusively on Warcraft 2, 3, C&C, Generals, etc (ie all RTS) and never felt that my use of a trackball was a problem. Emphasis on Never.
Contrary to what lots of people say, I actually think I would have not enjoyed gaming so much if I was using a mouse. I don't like having to pick up a mouse and move it around. I like having a pointing device that is always in the same place, which I can choose to control with just one finger if I wish to.