Upgrade went mostly without a problem (had set more than one Hostname for a service before, seems to not work anymore lol), and i have a pretty large configuration that has grown over the past two years.
What i noticed is that it is quite a bit faster. Also the dashboard shows a little more information than before and the logs have colours now.
Not necessarily just yaml — there are things yaml cannot do well, but even ignoring that, traefik can also use toml, or container labels — but rather, the entire concept of infrastructure as code is way better than GUIs. Infrastructure as code allows for much better linting, testing, and version controls thereby providing better stability and reproducibility.