Well, I bit the bullet and tried the A+ firmware (M218A++27firmware.rar) since I already had problems with B. It was successful! Thanks for the tip on setting the language! Since I set it to (3) Espaņol, it came to (3) English after the upgrade. I wonder if the language setting was causing the crash with firmware B (since the jetBook default, English, is setting 5, which doesn't exist). Here's a quick report.
1) I did not try restore original settings, and so, I retained my recent readings in my PDF files (not ePUB, which is not supported anyway).
2) The initial bootup after firmware update took a LOOOOONG time. The screen just sat blank (better than the TV fuzz I saw before) and I was afraid I bricked it. But after 5+ minutes, it finally came to. Much faster for subsequent boots.
3) Most of the interface is similar to the jetBook. However, PDF can do variable zoom from 1% to 6400%. Nice! PDF page turns seem faster, really almost instant for me.
4) There's an "ENEWS" option in the bookshelf-menu (see Cadion's picture) -- any idea what this is for?
5) MP3 player can do a playlist, shuffle, repeat, etc. I don't recall seeing these on the jetBook.
5) While browsing the eBooks, the size of each file is shown. Slightly different look.
6) Only page numbers with no "11.67%" or battery indicators like the jetBook while reading.
7) Apparently there is an English text-to-speech option?! I haven't tried it out (since I don't have any text files) but I will soon.
8) A few other options in the settings, such as screen settings, etc.
9) File manager is much more robust and offers several more options.
10) Apparently running Linux kernel 18.104.22.168 (Display info in test menu).
I'll keep you posted if I find out anything else!