I haven't done a battery test yet, but all signs thus far point to very good battery life. I had it connected to my work computer yesterday for several hours in the original firmware for copying music from it, so it was fully charged. After a 45 or so minute commute home yesterday, a 45 minute run (listening to lame v5) this morning and about 100 minutes of commute (listening to an audiobook, mp3, mono, 22KHz, ~53k bitrate) today -- it still says battery @ 84% under the system menu. I don't know how accurate that reading is, of course.
Will try to do a battery test this weekend, if possible.