Hey dsmid, I have to say I love this hack. It's useful and works very well; thanks for it!
I wanted to alert you that downloads from Google books do not work, for some reason. Take
Treasure Island for example. I browse there on my Kindle, click download, PDF, and enter the code. The browser says it could not be downloaded, but FreeDownload does not download it. There's nothing in the log (I have logging enabled, it showed other downloaded files fine). No error, just nothing. (EDIT: Forgot to say, I have the config set correctly. I can download PDF's from other sites with no problems.)
I have a Kindle 3 with 3G, firmware 3.1, FreeDownload 0.3, jailbreak 0.4, and screensaver hack 0.18. Think you can make Google Books work?