The KDevelop team has finally released a stable version of KDevelop 4.0 for C++ programmers.
This 4.0 release is a complete rewrite from the 3.5 version and several features were dropped in favor of focusing on making KDevelop a "C++ IDE instead of trying to integrate lots of languages and features halfheartedly."
According to the release announcement, "KDevelop 4.0 has an excellent C++ code understanding engine, which allows the IDE to understand your code better than you do, and which is then used to assist you by releasing you from tiresome tasks."
KDevelop includes the following features: code navigation, code completion, coding assistants, Qt support, project management, debugger, documentation and plugin support for other languages such as PHP.
You can download the source code here.