the only profit at the moment is that you can backup your nand (+keys!) on 4.0 without having a modified IOS. of course you can't use this image to unbrick your wii via bootmii, but you would at least be able to use an external nand programmer to reprogram your nand if you get bricked.
bootmii as IOS will make more sense when the first apps specifically made for bootmii come out, as it will be the only way to get apps based on MINI to work.
but for now, all you can do is a nand backup with the IOS installation...
