Salesforce puts a lot of effort into its desktop and Salesforce1-based mobile UI. These declarative UIs are the first to see advancements, one recent example being the ability to embed reporting charts. These standard user interfaces are also the primary method by which your subscribers will customize your application's appearance. Furthermore, with Salesforce's frequent updates, the UI will evolve even without you updating and releasing changes to your application.

For these reasons, you should ensure that, for all objects in your application, you make the best use of the standard UI by ensuring that your packaged layouts are highly polished and make use of every last drop of declarative features. It is even worth considering this practice for those objects that might be typically accessed through Visualforce pages. Considering the standard UI as a kind of primary or default UI also ensures that the validation in your Domain classes is complete, which...