Mike, it is very likely that firmware will NOT change for a while, anyway not in release v1, only JS files will (those, stored in internal memory, means, when release comes, you don't reflash, but simply copy the files).
If you:
1) are satisfied with features current firmware provides and i.e. don't have to mix it with other hacks
2) have Sony PRS 505
3) have firmware version 1.1.00.18040, or don't mind changing to this firmware version
You can easily install it. Follow these steps:
0) Connect your reader to your PC/Mac
1) Copy "database" folder from the release archive to internal memory (you should get /database/system/PRSPlus.js file and /database/system/PRSPlus-addons folder)
2) Download and extract my version of igorsk's flasher
http://prs-plus.googlecode.com/files/flasher-igorsk.zip (remove any existing before you do it) to your SD card
3) Copy new_opt.img from release archive to SD card root
4) Disconnect the reader
Igorsk's flasher interface should show up.
5) Press 4
It will take a couple of secs, then you should see the message that image file was successfully copied to /tmp
6) press 6
It will take a minute or so, and ebook will be flashed and then will reboot.
7) Now you have flashed ebook, you can remove igorsk's flasher.
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If you want to replace default fonts, first follow the instructions above and flash the reader. Then copy your fonts to:
files.505.1.1.00.18040\opt\sony\ebook\FONT\
on SD card. Disconnect the reader from PC/Mac.
1) Press 5 to create a new image with your custom fonts
2) Press 6 to flash
That's it.