Hi Atreju,
to have the standard (don't show Grub at boot) that I had when I started without a Grub menu (Ubuntu Mate 15.04 Beta 2), you should have the following settings:
Line 7 should be = GRUB_HIDDEN_TIMEOUT=0
Line 8 should be = GRUB_HIDDEN_TIMEOUT_QUIET=true
Line 31 should be = #GRUB_DISABLE_LINUX_UUID=true
Please make a screenshot of your current setup if the above doesn't work for you as they are the only setting changes I made!.
You should have the same as this which is what I started with before any changes:
