I'm in the process of catching up on several very long threads over at xda as well as reading on the Samsung knox website. So far, it seems that if the knox flag is tripped, it's irreversible and results in the warranty being void as well as the knox framework not working. If you had no intentions of using knox, then no problem. however, if you have a problem and require repair, Samsung may not repair the phone under warranty. It's not clear if the warranty policy applies everywhere, because some countries apparently do not allow the manufacturer to cancel the warranty for rooting the phone.