<p>I've used a Continuous Integration server in the past with great success, and hadn't had the need to ever perform a code freeze on the source control system. </p>

<p>However, lately it seems that everywhere I look, most shops are using the concept of code freezes when preparing for a release, or even a new test version of their product. This idea runs even in my current project.</p>

<p>When you check-in early and often, and use unit tests, integration tests, acceptance tests, etc., are code freezes still needed?</p>

I think that code freezes are important because each new feature is a potential new source of bugs. Sure regression tests are great and help address this issue. But code freezes allow the developers to focus on fixing
currently outstanding bugs
and get the current feature set into a release worthy state.
At best, if I really wanted to develop new code during a code freeze, I would fork the frozen tree, do my work there, then after the freeze, merge the forked tree back in.