I've got a Sony MZ-NH700 and think it's fab. I've only had a problem once with it not charging properly (and that may well have been my fault). Once charged it seems to last about 10 - 14 hours on play back. When recording I generally use it plugged into the mains and it's certainly lasted well over two hours non-stop recording. Alkaline batteries last for ages on play back.

I use a stereo mic I got off a dealer who makes his own for about £25 (which works out at about 1/4 of the equivalent Sony mic) and works more than well enough for my needs.

Darren