The article is pretty much spot on. For most people who want to write great software, the client side is currently a mess.
Phonegap => not so much; most just works like shit, but you only have to build once for a lot of platforms. It's a big reason for the proliferation of extremely bad apps in the Play store though; just wrapping of a website or form and putting it in as app.
Also any time you are using 3rd party tools like Titanium / Xamarin to develop these apps it comes with gotchas / limitations that may not even be worth it in the end (it seems like Xamarin has less gotchas). The main issue is that you still have to do UI twice in the end (iOS & Android), and one more time for web.
I don't know, what's bad about these http://xamarin.com/apps , e.g. Rdio which I've used and is fine?
Xamarin is a binding to Cocoa and other libs, it doesn't recreate any UI itself. So the "don't come close to natively built ones" doesn't even make sense from a technical standpoint. Not to mention that C# is compiled AOT.
>The article is pretty much spot on. For most people who want to write great software, the client side is currently a mess.
The article isn't even about those people in the first place. He even laments that "UX-quality bar on mobile is high" as a reason why mobile sucks.
As others have pointed out, Xamarin provides C# bindings for the native APIs. It is fundamentally different to Phonegap, which takes a lowest-common-denominator Java/Swing approach.
Out of those, I use Rdio daily and played Bastion a lot and they work great. I didn't know they were made with Mono until now.