Just wanted to report on my exerience to date using Energizer lithium
batteries in the Book Port:
They seem to last forever (100 hours?), and then die REALLY abruptly. Unlike
alkalines, NiMH or even NiCads, lithium batteries don't seem to give users
any advance warning that the batteries are nearing the end of their useful
life.
I was listening to an MP3 this morning, and the battery status said "100%".
In the middle of the song, the song was interrupted by the Book Port warning
me to replace the batteries.
My best all-round experience has been with Sanyo 2500 mAh NiMH batteries,
since there's a nice combination of longevity and environmental
friendliness, but you can't beat lithium for sheer longevity.
Peter