Interesting question.
I put over 80,000 miles on each of my last two Mustangs (85,000 on my 1995 GT Convertible and 82,000 on my 1996 Cobra Convertible) before selling them. I had absolutely no problems with either one of them and only sold each of them because I found another Mustang that I wanted more. The 95 GT was sold when I found the Cobra, and the Cobra was sold when I bought the 2007 GT.
My opinion, based on my personal experience, is that they hold up just fine. Now do they hold up as well as a Honda? Probably not. Honda makes very well engineered and reliable but boring cars (with the exception of the Acura NSX). I've got nothing against them but just would probably never own one. This is coming from someone who drove nothing but Nissans (280Z & 300ZX and two trucks) for 18 years before buying a Mustang. Now my driveway has one of each from the "Big 3" -- the Mustang, a 2005 Dodge Magnum and a 1999 Chevy Blazer, and nothing from Japan. I did nothing but brakes and tires to my previous Mustangs. In 50,000+ miles the Magnum ate an AC control unit (replaced under warranty) and the Blazer went through a water pump at 94,000.