Why is it so bad - I suspect they just hired some new BIOS programmers and the new guys are still finding their way through the source code.
Also, lots of bad reviews are in fact the user's fault - people doing their first build ever, getting some things wrong, not realizing it.
But anyway, it's safer to get a board that doesn't get so many complaints. Or wait until Gigabyte fixes the BIOS. Personally I'll stick with Asus for a while.
Do you like the Asus Maximus Z87 Hero?