RTV is an interesting proposition, and the old Orange server toyed with it for a long time. It was nice in that people got to choose maps/move maps when they didn't like it.
However, you also ran into people rocking the vote BACK to a map people just left, or constantly using rock the vote to the point of annoyance. We found that the best bet could be either an end-of-map vote, or simply a solid rotation of maps that are very well liked.