Sure there are some proprietary file types like Visio VSDX or other Visio template files, that it is not currently capable of displaying but for the most part this is an awesome little viewer that can be used in a pinch to view almost anything. Whislt some files are not designed to be viewed the application recognized certain file types even if it cannot view them. I had success with PDF, Word DOC & DOCX, Excel, PowerPoint PPT & PPTX (scroll and view all slides), JPG, RAW, GIF, PNG, ICS, PAGES, ODT, TAR, TXT, TIFF, ZIP, RTF, MOV (playable), m4a (playable), mp4 (playable), mp3 (playable).
Drag and drop files to the 'Open All Files' window to view file contents.