I have not, though I heard that it's possible.
The new firmware can reflow PDFs, but not as stable as this one, as far as I know. I'm happy with what I've got, so I'll hardly try the update.
Also, for those who still have their doubts: the pосkebook firmware supports additional interface languages and dictionaries. More details can be found on the PB forum, I believe. Also, some nice things to look at: http://www.pocketbook-usa.com/support/pocketbook-301/