I wouldn't touch one without annual inspection records. If nothing else, that at least tells me the owner intended to take care of it.
I was thinking about buying one this year as well, but decided to push that off for another time and make other investments. But when I was thinking more about it, I was determined I wouldn't buy used because I don't know if the last owner ever rigged off of the boom. A few years ago, there were several failures in a relatively short period of time (at least making news about the same time) - and at least some of those were attributed to rigging off of the lift. Just my $0.02. Its easier to say when its somebody else's money...