We use them a lot, but in my case mostly on the back end. We have a 24/7 service that runs and our customers depend on our service being up to make money. So if

We use them a lot, but in my case mostly on the back end. We have a 24/7 service that runs and our customers depend on our service being up to make money. So if a new feature or change goes out that has any risk, we feature flag it so that if there are any problems we can flip the new feature off immediately rather than have to wait for a fix and deploy, or wait for a rollback. Our feature flags are nice to work with in that you can just add them in code. If the flag doesn't exist in the DB, it is created with a default value. This makes them pretty painless to work with for us. You can activate feature flags one server at a time as well to roll things out gradually if you want. We have a simple web ui in our admin site where you can see them, what they are set to, when last updated etc. A good idea which we haven't done yet, is to log who changed it each time, and why as well. Being able to find flags that haven't changed in a long time is useful to identify ones you can clean up.