Ranked in these QuestionsQuestion Ranking
Pro The ability to create and edit files on the web UI gives GitHub pages the same power as a small CMS
One of GitHub's features is a very powerful web editor which helps users edit or even create files right from the web browser, once the file is saved it's the same as a commit. Coupled with pages, this tool becomes even more powerful, giving users a free CMS that is easy to use and create.
Pro Supports Jekyll
A simple, blog-aware static site generator, Jekyll makes it easy to create site-wide headers and footers without having to copy them across every page. It also offers some other advanced templating features.
Pro Supports custom domains
A custom domain can be added by creating a CNAME file with the necessary domain in the root of the repository and adding/changing corresponding DNS entries.
Pro Free tier
Static websites can be hosted on GitHub Pages for free as long as the repository is public. Private repositories start at $7/mo.
Pro Allows for all the git features when building your site, too
Con Unable to set cache expiry, must accept GitHub defaults (which are short)
Low cache expires - GitHub sets the cache-control: max-age header to 600 seconds, or ten minutes. Normally, you would set this value to a year so that it stays cached, and then use fingerprinting on your assets. Instead of serving style.css, you would serve something like style-62c887ea7cf54e743ecf3ce6c62a4ed6.css. As it stands now, assets are rarely going to be cached on repeat visits.
This will give a low score on https://developers.google.com/speed/pagespeed/insights with a 'should fix' recommendation around 'Leverage browser caching'.
For a high traffic site this may have implications