ok, here's the real deal. Among 1g and 2g iPods, small amounts seem to have been shipped with batteries that were faulty. Apple did a bad job of dealing with this, there were a lot of reports about people only getting a couple hours battery life, or the battery going completely flat in time. This didn't happen to the majority of people, I've had two 2g iPods now and both have had superb battery life, from day one i could get 8-10 hours at heavy use (switching songs a lot, using iTrip). But, Apple should have been better at replacing this minority of bad batteries.
Since then, Apple has switched both battery type and manufacturer, and the 3g and mini batteries seem to be holding up. As to replaceability. Apple did not make these batteries replaceable, for one simple reason: adding a battery door, and separating the battery from the rest of the components, would have made the unit signifigantly larger (i could see a half-inch thickness or more added), and the batteries are good enough that with a reasonable useage, the iPod will last 5-8 years, in which case the user will probably have outgrown it anyway. But, just in case, Apple is now offering a battery replacement program, to alleviate these concerns-- the iPod naysayers seem to ignore this. And now not only can you get a new battery installed from Apple, you can buy one for $50 that you install yourself, not a bad deal at all.
Lastly, no one was ever deceived about the battery, the literature that comes with the iPod clearly states that the battery is good for approx. 500 charge/discharge cycles. So, if you use your iPod 10 hours a day everyday you'll still get 1.5 years of life before you need to spend $50, which i'd say is tremendous-- who could use an iPod that much? Maybe a DJ but not an average user...
in short, the fears about iPod's battery problems were once justified, but everything's OK now.
paul