At work we use to use feature flags a fair bit, but switched to using branches instead for development. For our testing environment, we can access individual b

At work we use to use feature flags a fair bit, but switched to using branches instead for development. For our testing environment, we can access individual branches as subdomains to a testing environment. This lets the in-progress code be separate from the mainline trunk, while also letting other people easily check out a new feature in a testing environment. Only once or twice have we used 'feature flags' for trunk code; basically when the feature was ready to go, but may not wish to be activated until the last minute etc. I can definitely see the advantage though of having feature flags for very high volume environments like Facebook to 'soft launch' projects (eg, to just staff) before making it live. It's important though for code maintenance that you remove the feature flags after a while (once a project has settled in and won't be turned off), otherwise it can start to become a maintenance problem.