I have installed Ubuntu 16.04.1 alongside windows 10, everything works perfect unless gnu grub menu 2.0.2 takes too long to boot, there is somewhere 15-20 sec black screen till purple grub menu shows up.
It is ASUS k501ux laptop with PCIE SSD and it always boot very fast. it is loading windows in 13 sec and Ubuntu in 8 sec but that grub menu takes too long. sometimes it loads perfectly as soon as I turn it on but mostly that's not case.
Otherwise both Ubuntu and Windows load pretty quickly after I choose it from Gnu grub menu, problem is loading time of gnu grub menu itself.