But even in established languages I've had trouble finding an appropriate xml parser and had to tweak them way more than I thought necessary. I haven't (yet) had that problem with JSON.
Maybe it's just that I work mostly with JVM languages (Java, Groovy, etc.) but I haven't had any problems with handling XML - including Atom - in years. But I admit that other platforms might not have the same degree of support.
Most of my experience is from Python. Each time I use it I have to look at the docs for etree (a library that ships with Python). We would hit performance and feature support issues with etree and tried lxml but had binary compatibility issues between our environments.
The Hitchhiker's Guide to Python[1] (a popular reference for Python) recommends untangle[2] and xmltodict[3], neither of which I've used.
I feel like in other languages I've used had similar brittleness when dealing with xml. I might be biased because working with xml in an editor it's difficult to validate visually or grok in general when used in practice.
Oh yes, I've used Beautiful Soup, too. If I remember correctly I had great luck with html, but issues with xml. It also is only a reader, not a writer.
