I think Tim O'Reilly's argument is pretty silly actually. Here's my response: http://bit.ly/v6Adhu (re-printed below).
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I understand what Tim is saying, but I disagree that it's time to start over.
With Mac OS X, Apple definitely seems to have begun heavily focusing on feature development over refining existing UX. But the claim that successive releases of OS X become more user-hostile and encourages more lock-in is a bit of a stretch.
Apple has never developed for the power user, and they never should -- this is part of what makes their products so great; their unrelenting focus on the common case. In fact, complaining about a hidden library file for Mail.app misses this point entirely. It's actually a wonderful feature, since the common user is more likely to mess up their own mail library than to have a need to move it between disks.
+Tim O'Reilly's second point is valid, though, the UX for emptying the trash can definitely be improved. But again, is the common case deleting 400,000 files? Is the "delete whatever you can checkbox" too odd for a normal user to understand? Let's take the mom example; if your mom emptied the trash after deleting a file, would she want to know if it couldn't be emptied, or would she be OK with it being emptied without her recently deleted file actually being removed?
People can yell for a OS do-over all they want. The fact remains though: Apple focuses on UX more than any other company I know. If that UX doesn't cater to your particular needs and you'd rather have power-user flexibility and features, even if it means less polish and more annoyances when dealing with common tasks, use Linux or Windows. Or, better yet, just learn to use the Terminal and you can have the best of both worlds.