The first test rebuild of Trusty Tahr was started last week for all architectures (main component only). It is still running for arm64, all other architectures did finish the test rebuild.
Results can be seen at
http://people.ubuntuwire.org/~wgrant/rebuild-ftbfs-test/test-rebuild-2014010...
The archive for the test rebuild is https://launchpad.net/ubuntu/+archive/test-rebuild-20140108/
The test rebuild was done with a change which is not yet in the archive, changing the default Python3 to use the not yet released Python 3.4. These packages can be found in a ppa [1]. Please ask on IRC (#ubuntu-devel) if you are in doubt that a build failure is caused by the changed Python3 default.
Additional build failures for packages in trusty-proposed (not yet in trusty) can be found at http://qa.ubuntuwire.com/ftbfs/
Please help fixing the build failures for the final release.
Planning the next test rebuild for amd64, i386 and armhf for all components for the next week.
Matthias
[1] https://launchpad.net/~ubuntu-toolchain-r/+archive/python3