Been using a U.S. English version of Sony's DPT-S1 with 1.3.x firmware for a few weeks and have some thoughts to share.
The short of it is that I'm happy to be using one.
The following are some details covering info that I didn't find elsewhere before purchasing. May be this will help for other folks who are considering Viewer
The "Table of Contents" for a PDF file is usable unlike (AFAIU) for Amazon's DX. It works like this:
-with an appropriate PDF displayed, press the menu button followed by the table of contents button
-along the left side of the screen there should be an area displaying some table of contents entries - the area to the right of the table of contents entries displays a smaller version of some page in the PDF
-if an entry has any children, this is indicated via a different icon to the left of an entry's text
-touching an entry with children leads to all children entries being displayed (but they replace what entries were displayed before) - the area to the right of the entries is updated to display the corresponding page of the PDF
-touching the page causes the table of contents area to disappear and the full-size version of the page is displayed instead
Apparently no clipboard - no copy / paste -- however, this may be possible from firmware version 1.4.x (at least in jp version) - long-pressing a word in a PDF does bring up a menu with items 'Highlight', 'Search', and 'Google' though
Doesn't seem possible to flip pages while zoomed in -- however, apparently possible from firmware version 1.4.x (at least in jp version)
Although there are 4-page and 9-page views, there doesn't appear to be a dual-page viewFile Transfer
Both the internal memory and the micro SD card are accessible as mass storage devices -- I've only tested under *NIX, but don't believe it's any different under other operating systems -- no extra software necessary to access one's content (given which company made this device, this was quite a (pleasant!) surprise for me)
Have successfully removed and replaced the micro SD card while the system is in standby mode -- not sure whether this is safe...Browser
Doesn't appear to let one view HTML files that reside in internal memory or the micro SD card
Doesn't seem possible to view pages rotated (though that works for viewing PDFs)
Didn't expect to use the browser functionality, but as slow and limited as it is, better to have something than nothing - too bad it doesn't seem possible to save the current page as PDF (like one can do in FF)
Appears to limit one to using up to 3 windowsMiscellaneous
The current time doesn't seem to be displayed anywhere useful -- I actually did a search via the browser to find out the current time once...
Pressing the menu key while at the home screen
displays the current time in the top left corner of the screen
The UI smells of Android here and there:
Did not find a way to transfer files between internal memory and micro SD directly
Doesn't appear to be any auto-cropping of whitespace
Wikipedia's 'download as pdf' and 'create a book' functionality seems particularly useful -- though haven't found it convenient to access that functionality via the device itself...some of the created PDFs turned out pretty decently
Didn't expect to use the stylus to create notes, but much to my surprise I've come to use it -- I could just barely adjust to the lag -- now it doesn't bother me too much -- I used to dream of having a white board where I could restore the content...this device reminds me of that forgotten dream
Didn't expect to use the workspace feature (basically one can 'save' a set of tabs and name the set) but though there are various things that are wanting it's a fair bit better than nothing
That's it for now. May be I'll update this from time to time...