The HN convention for older articles is to append the title with the year.

    Finally something that explains Rails architecture [2007]

Finally? This was posted in September of 2007. You can see the section under "The Rails Way" used in a large number of plugins and gems, as well. The pattern is no secret.

That said, it is a nice article. It's just not new.

There's been a fairly large refactoring/re-architecting for Rails 3, including, unless I'm mistaken, avoiding alias_method_chain.

(I want to say that this whole pattern or ruby-ism is now being avoided in Rails proper, but that would only be hearsay based on something I think I read many months ago. ... Yehuda?)

I mastered a little about Rails internals by looking at the source code (of the framework), changing some methods (and entire classes) sometimes and by reading the development mailing list, I recommend the same way of learning for everyone working with Rails. Anyway, it would be nice to have an article describing the changes Rails 3 will bring to this architecture.

It's a good article, but it's pain points haven't been valid for a long time. Also I believe rails 3 relies less on alias chaining and more on rack middleware.