I think I have found why it's not working for you.
5.14.0-0ubuntu1 is still in the proposed section of the software repositories. If you disable the proposed selection in the software sources and then run the install commands it should then give you the option of installing
Open the Software Center and in the Edit menu select software sources then click on the updates tab....
Remove the check from the Proposed box.
Then in a terminal run
sudo apt-get update
After the update is completed try to run
sudo apt-get dist-upgrade again and it should show you that unity
5.12.0-0ubuntu3 is available.
Just a note, it is safer to not select the Proposed updates unless you need some program that is not available in the current release. The Proposed selection will install as updates all the newest programs, but they are the programs that are still in the testing phase so they can have some bugs still. Once the programs that are in the Proposed section have been fully tested, they will be moved to the Updates section and be available as a stable package.
untiy-revamped ppa lags behind the release a little bit, I believe that it was about a week the last time but he seems to do a good job of keeping it updated(as far as I can tell anyway, this ppa has only been running a short time)
As an aside, I have been running
unity-revamped and have had very few problems with it, the dodge windows feature occasionally sticks and will not hide the launcher but it is fixed by logging out and back in. This only happens once in a great while and everything else works fine while it is stuck....
Edit: the above mentioned version of unity (
5.14.0-0ubuntu1) is currently the recent version of unity so
5.14.0-0ubuntu1+ikarosdev2 should install correctly (as of Sept 2012) but this answer will still work if you have the
proposed repository selected and are getting a similar error but with different version numbers. i.e. this will occur any time a new version of
Unity is installed from the proposed section but the
unity-revamped ppa has not bee updated to the newest "proposed" version.