Roughly one and a half year ago we at the rsyslog project started to get serious with CI, that time with travis only. Kudos to Thomas D. "whissi" for suggesting this and helping us to setup the initial system. In aid of CI, we have changed to a purely Pull Request (PR) driven develpoment model, and have made great success with that.
Over time, we have added more CI ressources (thanks to Digital Ocean for capacity sponsorship!) and begun to use Buildbot to drive those. Buildbot is a great tool, and has helped us tremendously to further improve software quality. Unfortunately, though, it does not offer as close integration into (guthub) PRs as Travis does. This resulted in a workflow where we had all PRs initially checked by Travis and, if all went well, I manually merged them to master-candidate branch, which Buildbot monitored. In those infrequent cases where the buildbot tests detected problems, I needed to manually contact the PR submittors. This worked well, but required some effort on my part.
The past two week we designed and implemented a small script that integrates github with buildbot much like Travis does. In essence, a new PR (or an update to an existing one) now automatically initiates the buildbot build AND the result is shown right on github inside the PR. That's pretty sweet as it a) keeps submittors informed of everything, b) provides even better coverage of multiple platfrom testing and c) saves me from a lot of manual labor. Note that at the moment we see some infrequent quirks from this system (like some buildbot slaves not reporting, probably due to temporary network issues), but it already works much better than the old manual system. Also, I still have the capability to check things manually if there is a quirk.
As a consequence, we will change the workflow once again, removing master-candidate branch from it. Now that each and every PR is checked with all checks we have, there is no need to have an interim step when finally merging.