I use a Zoom H2 - mainly as quick, convenient way of getting musical ideas down and as a rehearsal/practice aid. For these purposes it's ideal but obviously they aren't demanding applications qualitywise - perhaps comparable to your family history interview requirement. I wouldn't have any hesitation in using it for high quality work but would want to use external microphones with it. Not because the built-in ones have any serious shortcomings (though they obviously can't compete with anything approaching a professional standard), it's just easier to get the placement right with external mics. That may be a consideration for recording live gigs but if you could get a signal straight off the desk it would make life a lot easier.I don't have extensive knowledge of all the recorders available but I get the impression they're all very capable. I'd just pick the one with the best facility match to my needs.
The sound quality was phenomenal.