Zoom is done! It took me about a week of intense development, which translates to perhaps 8-10 hours of full-time work. Most of that was spent trying to figure out why prototype.js's Ajax.Request wasn't executing RJS commands sent back to it.
For the past year, I've been concentrating on automating the process of converting two directories of 180ish hastily-taken images into a single automated list of images that are appropriately orientated, reduced, and titled. Although this is not core to collaborative manuscript transcription — it would probably be unnecessary for a 5-page letter — it's essential to my own project.
As a result, the page transcription screen is still rudimentary, but I've gotten most of the image processing work out of the way, which will allow me to return the diaries I'm capturing Real Soon Now. Completing the transformation/collation process allowed me to work on features that are user/owner-visible, which is much more rewarding. Not only is this effort something I can show off, it's also the sort of work that Ruby on Rails excels at, so my application has progressed at a blazing clip.
I've still got a lot of administrative work left to do in allowing work owners to replace and manipulate page images, add new pages, or reorder pages within a work. This is not terribly difficult, but it's not quite sexy enough to blog or brag about. Zoom, on the other hand, is pretty cool.