One thing not covered in the old thread was that while board feeds might give you a better signal (i.e. not clipped/over-driven) the mix is highly likely to be really funky because they are mixing for the house and not for a recording feed. Some crews will actually set up a separate mix panel for recording(rare). The hassle in doing this is you've got to split off each channel separately so one mix is for the house and one is for the recording pit and it just makes a lot more work/expense.

A friend of mine just pulled one of the very recent U2 shows off the torrent and it actually has pretty amazing quality for a recording some guy mic'd out of his hat! There are whole forums dedicated to concert recordings and such. It seems the typical method is some kind of hat-based mics into a PCM recorder (mini disk). There was one show in San Diego where they had 3 cameras+ other gear in the audience and they've mixed it down to quite a nice show. All that to say it can be done and with very acceptable results.

Google turned up some interesting links during my search.

Cheers,
Tim