Imagine, that you have float field with 2 symbols after dot.
At the views page with filter you need to filter values by all range of module of user's float input.
This article about colorbox and views: how to display first thumb styled image of the multiple image field and after click on it display all images in colorbox.
In most cases it is enough of functional of system_settings_form for saving settings and dont care 'bout submit ops. But what to do if it you need to add additional button to form?