This seems like a strange request, but for a few projects I am working on, it has been decided to use Github instead of Bitbucket.
Due to the fact I have no say in this, it means I will have to migrate from using Mercurial to Git...

Personally I like Bitbucket, but it would be great to 'synchronise' / import a Github project into Bitbucket and visa versa. That way I (and the few others using Mercurial) can stay with Mercurial, the rest of the people can stay with Git.