This is huge. We've wanted to use protected branches ever since they were announced but haven't been able to because we have hundreds of contributors merging to our primary branch every day.
This is great! We've been using protected branches with 100+ developers contributing and often face the out of date branch issue as our GIT implementors didn't realize this would be an issue until it was too late.
I can't wait for this to land in the enterprise edition. We go through some pretty convoluted steps to maintain branch protection while still allowing issues to be edited.