Though its a neat shortcut, a new member in the team who has not heard about the extension won't understand the code straight away. That's the problem of modifying the core behavior of a language/framework (often called monkey-patching).
That's an issue with every single piece of technology (operating system, library, application, API, programming language, CPU, non-trivial function or macro...). As such I don't think it can be a valid statement against the adoption of any specific technology. Besides, this particular concept is really easy to learn.
