So, I spent some time with Automator, Calibre, and MobiDeDRM tonight, and ended up with a nicely automated conversion process between Amazon and Sony. You'll need OS X 10.5, Calibre, and MobiDeDRM installed for this workflow to work, and you'll need to modify it to fit your LRF conversion preferences and specific environment (where you store your ebooks, where you put the MobiDeDRM scripts, what your PID is, etc.), but I thought I'd share it in case anyone else could find it useful. Note that you'll have to already have the Amazon files on your computer first - either through a file browser on a jailbroken iPhone/iPod Touch or through a backup extractor.
The program will take either single or multiple files from an initial file open dialog box, and then decrypt them using the MobiDeDRM scripts (which aren't included in this workflow, so you'll have to find them yourself and have them on your computer), convert them to LRF using one of Calibre's mobi2lrf command-line tool, and add them to the Calibre library using the calibredb command-line tool. I've left actually putting the files onto the Reader out of this workflow, so you'll need to use your favorite method for putting books on the Reader once it is done to finish the process. Hope this is of some use to someone else - I know I'll be using it a fair amount.
Workflow:
http://files.me.com/ahintz/3dr1b8