Fraying on the charger (dc-carrying) cable is definitely an issue, but my biggest gripe about these chargers is the form factor of the AC-carrying part of the power cord. I can't speak to non-US chargers, but the three-prong cord that plugs into the wall has no coiling shape. If the plug itself had a self-clip (like at the end of the charging cable), at least I could keep my cord from unrolling in my bag and expanding to fill the entire free space. I'm usually torn when I'm leaving the house with my macbook: do I bring the long cable and deal with bag disorganization, or do I hope I'm close enough to a plug and the plug orientation doesn't make me regret my lack of regular power cord?
You'd think with all this industrial design effort spent (pretty successfully IMO for the most part), there'd be an improvement in that particular cable.