No, the only way at the moment to get rid of the flashing demo notice is to buy a Demo Upgrade and go from Demo/F2P to ICE. We hope to change that in the future. We know it's annoying.
Jason, would a simple solution like changing font colour of "Demo mode" work? Black would be near invisible in that corner of the screen, and maybe you could make the font transparent altogether... Easier than going through all RoF accounts.