Superfeet in Inov-8 shoes? Ack! A significant design feature of the Inov-8 is the high level of flex. Superfeet would completely change the dynamic of the shoe for the worst.
I don't have plantar facitis, so I can't common of that other than to note that the flyroc has decent arch support for modest arches. If you have a high arch, you might want to look at other shoes. I would also note that there are a number of stretching exercises which is a highly effective treatment for plantar facitis.
Part of the design philosophy of the inov-8 shoes is to let your feet flex naturally. Initially this will give your feet a serious workout, but many people have found that once they have built up their foot and calf muscles, that inov-8 shoes rule.
I have more or less lived in the flyroc-310 for the last two years. I have several boxes in my closet just in case the shoe is discontinued... though the folks from inov-8 have said that they are not planning on doing the typically change shoes every so often, they will keep making the old shoes and slowly add new ones to the lineup.