I turned off sync, sound, turned brightness down, and generally wifi unless I've got reason to use it, still 'testing' how long my battery lasts. I only used the 'sleep' function for a couple days before seeing it just let my battery die so now I turn it off completely.
I don't know how well the sleep function works, seems like it might be bugged, I just don't have the time/interest in testing it at the moment.
As for complaining there is the bug report sticky, the wanted features thread (for a change/suggestion), and of course
http://www.pocketbook-int.com/ where you can send email to PB to make your POV known.