If anybody is using this and can share their experience, I would love to hear it. As far as I can tell the only other significant self-hosted CI project is Jenkins, and I'm interested in alternatives.
[0] https://drone.io
[Disclaimer: I work at https://circleci.com, a competitor]
One could argue that i.e. this/Travis/you is better at security then the average software company [it's probably true!]. But I still think many are more comfortable with keeping the source-code under their control.
Doing something like Github Enterprise for a reasonable price shouldn't be too difficult, I'd wager.
This is the primary reason we went with self-hosted bamboo and octopus deploy for CI and deployment. It does move managing the infrastructure of it all over to our side, but it could always be worse, I suppose (previous jobs not having any sort of structured deployment workflow, in particular)