His specific complaint was that he couldn't find the Library folder to delete his mail. Two things to keep in mind: first off, people who set up Mail extremely rarely will want to delete their email. So on the list of use cases to optimize for, that one lives near the bottom of the ladder. Secondly, the Library folder is, for all intents and purposes, something that should have been hidden to begin with. The kind of stuff that goes into a Library folder goes into hidden directories on other OSes anyway (think Application Settings on Windows, or .config, .gnome2, .kde on Linux). The fact that Apple only just now got around to hiding a folder that did nothing but clutter up the home directory for most users is significantly more surprising than the fact that it's hidden.
There was another complaint, which was that upon putting the relevant files in the Trash, attempting to empty it yielded file in use errors. That is indeed a problem, but he complains that he can't skip all of them, and that this is an old issue. So how this is related to OS X getting worse is unclear. It's definitely extremely annoying, but then I also don't think people find themselves deleting thousands of files of which several are in use very often. That said, one wonders what was using those files (unless he'd forgotten to quit Mail, but I doubt that).
Basically, “the latest frustration”, his leading example of something that is “worse in Lion than in Snow Leopard”, seems to not be a very good example at all. What's missing are the ”so many [other] things”. I want to hear them, because I haven't found too many, and I think it would be interesting to see what others genuinely think is worse. Some disagree with the changes in Spaces, for example, which is understandable. What else?