We do have excellent support for Mercurial in Bitbucket, Bamboo (which I am Product Manager of) and Fisheye. I can't speak for Stash but there is a lot of work

We do have excellent support for Mercurial in Bitbucket, Bamboo (which I am Product Manager of) and Fisheye. I can't speak for Stash but there is a lot of work going into it right now. It's still a relatively new product and both Git & Mercurial are important parts of many teams workflows, so we will have to wait and see.