Eh. There are different levels of monkeypatching. I have no problem with extending even a fundamental class with a new method if it's done with care, despite the potential downsides. I think the upside of monkeypatching can outweigh the downside when it facilitates tight, readable code (not that I'd consider the code in this post an example of that). The real problems show up when changing the behavior of existing methods, and that's where I think the downsides often outweigh the upsides.