I have at least one character on every server except Vigilance, Union, and Defiant. (I made one on Zukunft to brush up on my rusty German; what a terrifying experience. I gave up very quickly because my German was more than rusty... it was practically nonexistent!)
I started out on Champion but rarely play there anymore. My four 50s are on Justice, Virtue, Infinity, and Triumph. Justice and Virtue are my main hero servers, Infinity is my villain server. The smattering of characters I have elsewhere are mostly below 20 because I have serious "shiny!" issues...