I know there have been volumes about this...but I have not posted once about it...so here is my one shot at beating this dead horse. :-)
I personally would prefer a wipe. Actually, to be more precise, I am wiping my characters, even if they do not. The reason? I have played these characters like beta characters. Have taken chances with them. Tried different armor and weapons. I have followed one tradeskill...deleted them and then tried another. I am using the beta to get all of the knowledge I can so that when retail hits, I can make the best decisions and have the most fun with my characters. So...these toons that I am playing now are doomed.
Interesting point, though...I had fun just not caring about the long term abilities of these guys. My pally has done leather/skinning mining/smithing herbal/alchemy. I do not care to stick with one because I will never get him that high before retail. Lets me try them out.
As for fair...well, all of us in beta already have an insurmountable advantage in knowledge that no wipe will ever overcome. The day they wipe and start fresh, the beta people will hit each quest with precision, handle all drops accordingly...know exactly where to train for what and where to find drops. This fact alone will un-jam the newbie zones. Beta players will just plain level faster. And the graphics are so cool, the true newbies will be simply enjoying it and taking it all in (remember your first day in WoW? I walked around and looked at everything...ran into and out of every building. Talked to every NPC and laughed at all of the different replies...lol).
And lastly, even if they do not wipe, I am not worried about fair. I will still delete my toons and start fresh. It is not a competition. It is a game. To me, starting a fresh toon or two given all I have learned with beta will be the most fun for me.