I am experiencing the following Viewer Pane problems:
(1) The viewer pane window does not refresh an image when the file changes--even though the preferences menu item "Automatically refresh image when file changes" has been checked. This feature does not work on my laptop running Windows 7 Professional, nor on my desktop running Windows 8.1. 
(2) The viewer pane preview in Directory Opus 11 is much, much slower than Windows File Explorer for all types of files.
(I mainly need these features for viewing PDFs. My default PDF viewer is Bluebeam Revu Extreme.) 
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Which types of file are you seeing that with? The automatic refresh option may not apply to files displayed by external viewers, such as PDF files.
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Literally all types of files? Even JPG files, for example? Which PDF viewer are you using in Explorer; the same as in Opus?
The viewer pane's automatic refresh does not refresh PDFs. It does; however, work for TXT, TIFFs, and JPEGs. I am using Bluebeam Revu Extreme to view PDFs for both Windows File Explorer and for Directory Opus 11.
As for speed, the speed diffrence in previewing JPEGs is noticably slower in Opus, but for PDFs, it's much, much worse than Explorer.
Are the PDFs large or on slow devices/connection? Opus may be creating temporary copies of them in order to avoid problems with many PDF viewers blocking rename, move or delete operations while files are open in the viewer. Could that account for the PDF slowness?
The PDFs are full-page scans at 200 dpi ~ 150-330 KB per page. My connection is not slow and neither are my devices. I really like the features of Directory Opus 11, but my work requries me to scan a lot of documents, rename them, and edit them as PDFs; therefore, I need to be able to do so quickly, and to be able to preview PDFs after they have been altered--in other words, refresh an image. Is there a PDF previewer plug in that works in Directory Opus that (1) is quick, and (2) automatically refreshes the image if it is changed?
If you copy the same PDF file in Opus, is there any kind of similar delay?
Most PDF preview handlers should work identically inside of Opus and Explorer, except that Opus may create a temporary copy of the PDF before asking the preview handler to open it. (So if copying the file is slow, due to transfer speed or anti-virus scans, for example, then it could cause a delay.)
Adobe Reader is the preview handler we have tested with the most, but we've also tested with PDF X-Change and the FoxIt preview handler.
(If you're using a version of Opus earlier than 11.13, there's another thing which may be happening. I'm assuming you're on 11.13 or 11.13.1.)