I just upgraded my 64 bit AMD desktop Xubuntu to 14.04 after easy, successful upgrades of 2 other machines to Lubuntu. There were numerous errors during the upgrade and now it seem to be in an almost unusable state. I cannot
su without getting a segmentation fault and the Software Updater crashes. Skype doesn't work with Pulse Audio - no sound output.
I might add that there was a question about retaining the root privileges or replacing them during the installation. I tried to answer KEEP but was warned that this could cause problems so I answered REPLACE.
Also I saw something about encryption of the disk device and, if the key is different from the previous release this could cause problems.