Though I will say the biggest pain point with Wordpress is syncing and merging DB changes amongst team members, since so much of WP configuration is stored in the DB this becomes a real point of frustration especially on very large sites. I'd peg that problem as a much higher priority in terms of WP workflow than how to manage git inside WP admin.
Storing the DB state in GIT is going to be an issue with a site of any substance.
Thankfully there was a deploy.sh script on github  which could be used to deploy your plugin from git repo straight to wordpress.org's SVN repo. :)
Uh, what? Any medium/large site inevitably ends up with a few custom plugins.
Plugins are for adding functionality to your site, if you want a sitemap, there's a plugin for that. Not happy with your current sitemap? Install/Create a new plugin, replacing the old one. If your sitemap isn't working, where do you look? Your sitemap plugin's code.
The importance of having this separation of tasks, removes a lot of risks too in my opinion. If your site isn't working instead of risking having to change your theme, you can deactivate the troublesome plugin. Albeit finding the offending may be difficult, but at least you're not changing the total design of your site.
Hence why I believe in plugins and themes having distinct tasks. It really helped me organise the development, and maintenance of sites.
Here's a pretty decent setup for using git with WordPress too.
Versionpress sound like they're going to try something a bit smarter with the database file though.