I think he misses the point here that 'people like to have fun'. We know that skeumorphic designs aren't the most efficient and in some cases may confuse the us

I think he misses the point here that 'people like to have fun'. We know that skeumorphic designs aren't the most efficient and in some cases may confuse the user. But these apps aren't being used to control a spaceship. They are often used in the 5 min gap between meetings or on the train where a tiny sliver of fun is perfect. Whereas when I look at something like Kicksend it's just another boring, stale and uninspired photo site. And yes, it may 'get the job done' better but if I am not enjoying using it then why not use something that does. And that really is the crux of the argument here. You have a tiny window of opportunity to convince a person to keep an app before they will simply delete it and find something else.