APEX is a great tool, and how it often happens, you can achieve same things in a dozen of ways using it. That's great, but sometimes it's really hard to determine how to organize and structure your applications, because they tend to become a catastrophy with the speed of light.
Why care, if it still works? Because a well-structured application is much easier to improve even for different developers, it's much easier for them to work together when there're clear development guidelines. And I haven't even mentioned errors, which are much more likely to be made in a messy application.
I find all the tips really useful, but what is even more important is how coherently they are given. Seriously, guys, if only we had such guides on all aspects of APEX development, such as database architecture, business logic development using SQL and PL/SQL and version control, it would be ridiculously simple to start making world-class applications. Thank you, Vincent!