Mihawk's real reason ….
...., he let Zoro alive was, in my opinion more than just his appreciation for Zoro's courage :
let me explain my theory,
http://groups.msn.com/OnePieceMangav-3/volume6.msnw?action=ShowPhoto&PhotoID=1273
her you can see that Mihawk's intention was to kill Zoro, then
http://groups.msn.com/OnePieceMangav-3/volume6.msnw?action=ShowPhoto&PhotoID=1274
when Zoro used his most powerfull technique (an ougi - secret technique)
we saw (the last panel) Mihawk geting scared ( OK maybe not scared but there was a reaction)
I think he saw at that moment the real potential of Zoro and let him live.
Later we saw from Zeff's reaction that it wasn't normal for Mihawk to not kill his opponent, but it's understandable if it is because he saw a chance to get a worthy rival (like shanks) and not getting bored. Like we see Mihawk does things only to kill time because he was bored.
So here it is, I d like to hear some reactions
thanks for the time and Ciao