There are scenarios when you work with DVCS (like Mercurial or Git) and CDbMessageSource. To my experience keeping the development database and production database in sync can be very time consuming. Plus, when working in a team, you never know when the database was updated.
I have seen a couple of articles about how to integrate external libraries to debug our PHP code (i.e. firePHP) but after you read this article you will realize that there is no need for such libraries when using Yii.
Most applications will have one or two sidebars and often you want to control the content that should appear in the sidebar based on the action. For example you will want to show something different on the homepage as opposed to some view page. While achieving this you generally also want to avoid putting the layout into each view, as that would mean if you wanted to change the layout (e.g. put the sidebar on the left instead of the right or do some funky layout which requires an additional div tag to be added) you'd have to go through every view, which does not achieve good code re-use. It is also bad practice to have lots of if statements in column2 layout just so that you can generate the sidebar correctly.