With all the myriad improvements, bells and whistles added to various Linux window managers over the years and [without installing hacks or pluginsI I <i>still</i> have to open a file to find out what's inside it.<p>I'm no great fan of OSX's Finder. It has a list of flaws as long as your arm, but the ability to hit <spacebar> with a file selected and get a popup preview of its content, whether video, image, text or source code is something I use multiple times a day. Why, after all these years, have no Linux distros adopted this oh-so-basic feature?