You can preview a profile before you add it to your collection, and preview changes to existing profiles before you accept them.  You can also preview two profiles at once from the Add DVDs window, Add by Title.  Select two titles by pressing the spacebar on each, then select Preview.  DVD Profiler will preview both at once to let you see the differences.

Layouts may contain HTML Sections, one or more of which may be designated as suitable for previews.  If the loaded profile has HTML sections that are suitable for previews, then will display as an alternative to the default comparison in the "Preview With" entry.  You can edit these with the Edit button here or via DVD Profiler's main menu in View->HTML Windows->Edit.