Hi Kovid --- I just tried out the latest 0.8.17 version of Calibre with my new HP TouchPad. It recognizes the device, and successfully transfers the mobi files to the proper Kindle folder on the HP. However, the Amazon Kindle App for TouchPad is still in beta, and sideloaded files to the WebOS won't be detected by the Kindle App. What the transfer seems to be somehow inadvertently doing, however, is making the Kindle book navigation menus inaccessible so that it is impossible to do much other that read the current book you were on before transferring the files from Calibre. Not quite sure how to remedy the problem, other than an uninstall and reinstall of the Kindle WebOS app. I deleted the Calibre files I could find, but it didn't seem to make a difference.