That's weird. Nobody I know has ever made a successful Ubuntu version upgrade. There was literally no case where nothing broke.
I resigned; I will make a clean new install if I want a new version.
I know this is not the proper way to register a bug, but there's a problem when installing 14.04 on a UEFI motherboard that does not have Secure Boot. The installer just assumes there's Secure Boot on and the bootloader gets misconfigured.
Do you use the provided upgrade path? It's very surprising to me to hear that - we test upgrades pretty thoroughly.
Disclaimer: I work for Canonical.