We use Travis for Mac & Linux builds of OSS projects (e.g., https://www.telepresence.io). What's frustrating is that even the paid service for Mac is just as bad. We're on the East Coast, so we can use Travis for Mac in the morning, but it's terrible by lunchtime.

Fun fact: before Travis had multi-stage builds, we were able to get multi-stage builds in Travis by using the fact that mac builds were ALWAYS slower than Linux. So we could have our Linux builds create artifacts that were then used by Mac builds ...