Personally, what I want in a BL series is a good throwback (melo)drama, boarding school preferred, but optional. (I'm thinking something vaguely like Touma no Shinzou, which is about boy/boy relationships, but also has an excellent drama-suspense plot that is the main backbone of the series)
To be honest, I'm gettting a little (read: "very") tired of the goofy, shallow fluff that comprises 99% of the genre's anime efforts. Don't get me wrong, I have a guilty enjoyment of KKM, and I DO realize that this is a genre with a fairly steep crap:good ratio. Still, I often feel that more care is taken with a yuri series' mood (and budget!
) than there is with your oh-so-typical "slop it out, these chicks'll eat anything" BL series.