I didn't say it was a good experience, mind you, just incomparable.
During my last trial, which dragged on for six weeks before the judge finally put it out of its misery, I had just that experience. On her second day of cross, I learned that my client had made an audiotape of certain threatening messages left by the opposing party and one of her henchwomen at the start of the litigation. As the third attorney on the case, I'd not seen this declaration before. I had been blissfully unaware of that tape, and had failed to produce it.
Four days later, after searching every night after a full court day, my client finally found the blasted tape, and brought it triumphantly into my office. She had listened to it once at home, and said that it was pretty good stuff.
You know what's going to happen next, don't you?
We pop the cassette into the player, hit play, listen to an ominous few moments of message and then--squeal! flapflapflapflapflap!--the tape breaks.
One panicked hour later we have located a shop a few blocks from my office that repairs and duplicates audio and videotapes, no less, for the courthouse set. Another ten minutes, and fifteen mere dollars, later, I have a repaired original and four copies of the tape to produce all around.
The obvious moral of the story, other than keeping google at hand at all times? Copy your evidence before you put it in a tape player. It is much easier on the nerves.