I suppose it was a good PR move, but I wish Ubuntu hadn't added Docker to an official repository (albeit the universe one) yet, since Docker hasn't hit 1.0. Especially since Ubuntu is packaging it under the name "docker.io", whereas the official package is called "lxc-docker". Seems bound do generate confusion.
They can fix the name issue with a meta package, I've seen that happen a few times. Personally I'd rather they just leave a lot of this stuff to PPAs and external repos.
http://vagabond.github.io/rants/2013/06/21/z_packagers-dont-...
and its follow-up:
http://vagabond.github.io/rants/2013/06/21/zz_packaging-and-...
The Docker package in Ubuntu trusty (which comes from Debian testing/unstable) is certainly more Debianized than the official package provided by the Docker team. Whereas the official Docker binary is statically linked (and the build process has to go through some contortions to make this work), the Debian/Ubuntu build is dynamically linked. Consequently, the Debian/Ubuntu build has to run a separate "dockerinit" binary inside containers, whereas the official build uses a single binary on both sides. Naturally the official build is tested much more extensively, so I'd recommend using that.