It used to be easy to edit grub to change your boot order, default OS etc. Then it got hard (too hard), and now it is easier than ever:
How do I change the grub boot order?
It is especially nice to be able to hide more comples options under a submenu e.g. Advanced settings. Note – you can’t indent an option but if you shift it up into a submenu it automatically indents.
I recently needed to change a machine from Lubuntu to Ubuntu after a test installation. The main thing was:
sudo apt-get install ubuntu-desktop
But that left the log-in looking wrong. I tried:
sudo dpkg-reconfigure lightdm
… but that didn’t work (at least, not on its own). The solution was to change the greeter-session from lightdm-gtk-greeter to unity-greeter. See:
Lightdm autologin problem on Lubuntu 12.10
And being fussy I also wanted to change the default splashscreen to Ubuntu: