By replacing your system frameworks with those from a WebKit nightly you're going to see trouble with OS X software updates, system-wide instability due to runn

By replacing your system frameworks with those from a WebKit nightly you're going to see trouble with OS X software updates, system-wide instability due to running bleeding-edge code, and a test environment which isn't representative of what your users will see. If for some reason you need to use the frameworks from a WebKit nightly with your application, use DYLD_FRAMEWORK_PATH to point your app at the WebKit nightly's frameworks. This has the same benefit without any of the downsides mentioned above.