It allows the opening of raw files in other raw converters...normally when you do an Edit In from Lightroom, Lightroom renders a TIFF. With the plug-in you can bypass LR's rendering and open into another raw converter.
Jeff: Therefore, if I understand you right, if I modify (edit) my raw capture in Lightroom then seek to edit it further in Photoshop, Photoshop will see my Lightroom modified capture as a tiff. But if I use "Open Directly" I will be sending to Photoshop my initial raw capture, but NOT my Lightroom modified raw capture. Have I got it right? Thanks. Jim