Dallas has ESPN 103.3, There are other sports radio stations on the FM dial throughout the country, not sure if they are ESPN or affiliated with any network.
I think ALL sports radio stations should move to FM, in this day in-age, sports-talk is something people want and still need to come to the radio for if they want local sports talk.
Music stations I think would notice the hit in ratings and advertising is sports-talk were on the FM band.
So many times advertisers wont buy a 2.1 rated sports talk station b/c its "On AM, and we dont buy AM" but it its getting a 2.1 on AM, it would do a 4.0 on FM and out sell the 18-54 male targeted stations.