When reviewing PR, it has nice file/folder tree on left side, which is far superior compared to scrolling over 10+ files without context on Github, I hope Github gets this soon...
There's a browser plugin called Octotree which does a pretty good job of this, but I'd prefer it to be builtin.
Bitbucket has it as well. When you move from Bitbucket to Github your PR workflow in the WebUI feels utterly complicated and way harder to review.
I already started to use gh a few month ago and that finally puts some sanity into working with github. Beside of creating PRs and merging them you can also get the diff of the PR, and pipe it to other tools. In the most simplistic case into diffstat. That finally compensates a bit for the horrible WebUI experience. Still a tree view would be nice.