At my first company, we used Jenkins for all our CI/CD (Continues integration and continues deployment, though really we weren't continuously doing either of those). Jenkins seems like the standard go to for larger, older companies. While I found it serviceable at the time, I've grown to dislike it, looking back. Mostly because of association with bad practices at companies I've used it, and also some because it seems so gui focused.
I've used a number of other CI/CD frameworks since then. When trying to get a job at my second company, I set up Travis to do CI/CD on my personal website (which I had just redone). I found it so much simpler than Jenkins, if it was a bit less discoverable. I had something up and running (for free) very quickly, and then essentially never had to change it again. At my current company, we're using Concourse, and while it has a steep learning curve and can be really complex to do certain things, I very much appreciate it's unix philosophy inspired designs. (Everything is CLI based, infra as code, immutable etc).
I had previously toyed with Github actions when it came out, on the Smart Columbus project, but didn't dig too deep as I just didn't have a need. (My CI/CD projects were running on Travis without issue). However, when Travis decided to finally shut down travis-ci.org in favor of travis-ci.com, (or maybe the opposite, I'm still confused) I figured I'd just port to github actions instead.
Github Actions seem incredibly easy to use. Setting a flow up for Quest Command was painless, fairly quick to setup, and logical. While I miss some of the unixy design of concourse, and haven't created my own action yet, cannibalizing examples and tweaking them to meet my needs has been really easy and straight forward.
The integration with the rest of github makes github actions really convenient. It's so nice to create actions as part of your code base, to be able to easily leverage crowd sourced actions, and to be able to see the results in the same site, instead of having to coordinate with a second site for CI/CD. Secrets management works really nicely and as an added bonus, everything runs really quickly. In Travis I'd often have to wait in a queue for my build to succeed, where as with github actions I've not seen that (yet).
It's so cool to see github create and support a feature like this.