> FWIW Ubuntu (and others I believe) has been using it for quite a while, and it works great.
Except when it doesn't, or when it should do things differently (i.e. be configured in a different way), it's extremely difficult to find out how to do it. F.ex. is there documentation on how Ubuntu's integration with grub2 works in detail, so that one can tweak things?
There's a flood of howtos, forum posts, blog posts etc. Each outdated in its own way or covering only some specific aspect. A lot of howtos covering Grub1 and not saying so etc.