Limited Open Source support (only 5 repos) so I have decommissioned this on most of my GitHub repos now in favour of other CI systems like GitHub Actions, Travis CI and Azure DevOps which are my top 3 (in that order, I still use a lot of other CI systems too, see https://github.com/harisekhon for a tonne of them).
The Yaml is a bit ugly with capitalized strings and too many explicit options from the generated default template.
Lots of options do not appear in the yaml to revision control, which would be ideal.
It's own quirks, where builds may get cancelled or fail for random reasons that aren't my code, eg. upstream apt repos are temporarily unavailable (unfortunately most CI systems don't detect and retry this properly so you must do some retries yourself).
Badge could be nicer looking, like GitHub Actions, Azure DevOps, Circle CI, Semaphore CI or the shields.io badges (shields.io supports tonnes of CI systems but not Buddy unfortunately, otherwise I would have replaced the "buddy.works" badge in my README.md with a nicer constructed one with flexible text, formatting & icon from shields.io) Review collected by and hosted on G2.com.