I've been using a plugin called edit-author-slug. After installing Membership, this plugin doesn't work anymore. Do you know why there could be a conflict? Do you know of a work-around? This isn't super-critical for the site I'm working on but I've always considered giving away a person's true login name in the author archives view to be a serious security oversight on the part of WP.
By the way, I had to select the site above as the site in concern since your form would not accept "other" as a valid response to that field.