update-manager -d

No major problems.  I did have to manually remove a couple of ppa entries from my /etc/apt/sources.list.  Also, I changed from the generic ‘main server’ to a much, much faster (at the time) server.  The easiest way to do this is via gui, as far as I know.  Ubuntu will check for the fastest responding site if you use ‘System’ -> ‘Administration’ -> ‘Software Sources’ and ‘Select Best Server’,’ or use ‘Settings’ under the update-manager interface (‘settings’ is on the lower left) to get to the same place.   I shaved off several hours from my package download by switching to a server that had some combination of proximity, light load, and high bandwidth.   This involved a generous amount of luck, and probably the uneven demand associated with a pre-release version of the OS.