It would be nice to have an alternative way of browsing the source code (files), by showing all files in the repo on a single page, rather than requiring the user to drill-down into the subfolders.
A screenshot of how this could look like is attached.
We work with Magento modules a lot which tend to have a rather deep directory structure, so to get to the actual files one often has to navigate at least 5-6 directories down.
The attached screenshot shows how we customised our internal HgWeb interface (special theme+hacking HgWeb internals), but now that we are switching to Bitbucket, this feature is dearly missed by all. The screenshot also shows a great example of Magento modules often having more subfolders than files.
This feature could be a per-module or per-user setting.