If you are familiar with the Outlook preview pane in Outlook 2003 you will probably use the option to display the pane on the right of the message list rather than underneath the message list, especially if you have a wide screen laptop. This layout is much easier to use than in previous versions where the preview pane appeared squashed underneath the message list.

Unfortunately Mail in OS X does not have the ability to do this ( at least not natively ), however Aaron Harnly has released a plugin for Mail that delivers this view.

It works really well on my 20″ iMac. Recommended !