i've seen postings in various places online attesting that people aren't being charged for whispernet-delivered pdf conversions via their @kindle.com addresses. i went ahead and tried it for myself yesterday, sending over a Whole Bunch (TM) of pdf files for a class, so i certainly hope the anecdotal evidence i've found is correct! i remember some of those postings stating they had found something official-looking on amazon saying that the $0.10 fee had been removed, but haven't tried to find anything official myself, yet.
edit: the listing for kindle itself on amazon still says: "This allows you and your contacts to e-mail Word documents and pictures wirelessly to your Kindle for only $.10. Kindle supports wireless delivery of unprotected Microsoft Word, HTML, TXT, JPEG, GIF, PNG, BMP, PRC and MOBI files." i didn't find any official information about dropping the $0.10 fee, but i did find corroboration on thekindlechronicles.com, and kindleville.blogspot.com, where the writer says they specifically talked to kindle support about it and got confirmation that there would be no $0.10 fee. who knows? i'm choosing to act as if it's true, and you can bet you'll hear back from me if it isn't.
