What makes the 'Cat poo' coffee (Kopi Luwak) flavour worth drinking?
I've never drunk it (can't stand coffee myself), but the general theory is:


A wet ferment.  Some coffee producers have attempted to duplicate some of the processes with enzymes, as you've mentioned.
More likely to be picked closer to peak ripeness.  The animals have the advantage that they're picking berries to eat, and will pass over unripe ones to eat later -- unlike human processing which might just look to strip the whole bush.


In talking to one of my co-workers (also not a coffee drinker), and she said that she's had coffee right after it's been processed, and it was dramatically different from the stuff that was available in Europe or North America ... which leads me think that freshness might be a more important quality than some of the other aspects of the highly expensive coffee.  (unless you're talking about psychological effects)