It took another phone call and an elapsed time of around 9 hours, but Amazon finally unregistered the incorrect serial number from my account, and I was able to register the correct one.
Quite soon after that some queued elements were downloaded without any intervention and the unit was automatically linked to my Amazon account.
Tried a PDF conversion on a sample e-book I had – not bad. The Amazon service doesn’t appear to be doing an “intelligent” conversion of mapping the table of contents and so forth, but it’s readable.
After a little use, the screen is as good as I expected, and very easy to read.
There’s some (hidden?) shortcuts, too – prefix a search with “@web” or “@wiki” to search the web or Wikipedia. Web searches use Google.
IP traffic appears sourced through Amazon.
More time needed to evaluate form-factor and the user interface..