I'm not telling you anything you don't already know David, but Fowler and many of his peers and contemporaries grew up developing object-oriented systems that ran in large enterprises. You could read the title as "patterns we are using to build enterprise systems". That is primarily the market Thoughtworks continues to serve. Good code and design is much more broadly applicable, of course.
Fowler's writing is what makes the books so good: PoEAA is much more approachable than the GoF books. It's more approachable than his early books (Analysis Patterns).
I'm surprised that you didn't mention The Pragmatic Programmer..
I think that a lot of the people here (and who read your blog) could do worse than to check out "Team Geek". It's about people, not programming, but the impact it has had on me is equal to PoEAA..
I thought DHH hated people talking about "enterprise" and "patterns"