Firmware 5.15 for Inkpad 840 has been rolling out recently.
I got the update over the air a few days ago, here is the release note:
http://www.lesen.net/forum/attachmen...-pdf/?9a16345a
Overall it's a solid update that helps increase the speed of page turn when reading pdf files (especially with large/heavy pdf files).
I noticed one bug that was introduced with the update though, at least on my device: when long pressing the screen (to get a contextual menu/action), the long press is sometimes recognised as a single/short press. Never had that behaviour before.
I really like the increase of speed with pdf files however - I actually bought the Inkpad for its pdf handling capabilities essentially, which is still an unmatched killer feature two years after this device came to the market.