You can remove it by installing a system menu wad of whatever system menu you have. (I have 3.2, so I'd just install that wad)
Then you can run the hack remover to remove the hacks.ini that's in the flash.
However, for me, preloader is better than bootmii. Now yes, I'm aware that bootmii installs to boot2, but I'm one of the 10% that cannot install it there, only as an IOS. Personally, preloader has saved me from several banner bricks.
And with hacks on mine, it makes it that much better. Region free, disc channel moving, copying protected saves, disabling warning screen, I could go on.