there is a shuffle setting already to shuffle with the same or with a different artist bias, where you can set the bias high or low as you want. So perhaps i can add the same function for genre.
The only thing is people use many different conventions with naming genres so i dont know whether i would be able to do 'similar' genres - it might only be able to match on when the genre is exactly the same or not. Perhaps it could look for words in the genre eg. if the seed song has Rock then Alternative Rock would also match
with the Auto-DJ panel there is an option to select songs from similar artists (as rated similar by last.fm, and you also have the option to stream new tracks not in your library from last.fm)
So although not exactly similar genre, it acheives something fairly close i think