I have a Tivoli PAL. The battery life is awesome. Reception is remarkably good as well, although part of that may be due to the tiny size of the unit itself and the fact that it can therefore be moved around and placed in optimal spots for reception.
The sound...well...for a tiny box you can carry in one hand and run for hours on end without batteries, it's not bad. For listening to NPR, it's probably entirely suitable. It can sound a little plasticky at times, real bass can cause it to break up, and it's obviously missing the high and low ends of the spectrum (playing around with a sine wave generator I seemed to get useful response down to ~90 Hz and up to ~17 kHz, but the treble falls of rapidly as you move off-axis). It's mono (duh) so playing back spaced-pair recordings can lead to weird frequency cancellation effects. On the right kind of undemanding material it can sound pretty musical though.
Basically, as long as you don't buy into the reviews claiming audiophile sound, you'll probably be happy with a Tivoli for what it is. I'm certainly happy with mine.