@ Bob the ninja: I think you're correct regarding people underestimating the life of Li-Ion batts, but you may be incorrect regarding development:
http://wired.com/wired/archive/14.11/battery.html
this Wired post says that Li-Ion is at the end of its innovation days; they're still great compared to AA's, but not much more advancement of tech will be had.
Would love to see someone at MAKE magazine or some other 'modder' try to hack the battery compartment and throw in some replaceable. Me, I hate the things, and like the rechargeable brick, but that's me.
The best indicator of longevity and durability will be the display models, like Nightwing said. If the Reader takes off, and the display models are still performing well a year from now, that's a good sign.
Heck--if they're still selling these a year from now, that's a good sign!