As a daily Bitbucket user, I appreciate their efforts. But unfortunately I don't see improvement on navigation. It's quite painful to browse source code via web. If I just want to quickly look at someone's repository, I will make a lot of browsing, and it's just way too slow.
Compare it to Github's slick UI: https://github.com/blog/760-the-tree-slider
But I am optimistic Bitbucket will change it for the better.