I think 'feel fully native' is a misnomer. They are fully native. When you build for iOS you use xib or storyboard for layout (or native code adding views/subviews directly) and the same for Android, you use layout files.

There are lots of great apps out there, Rdio was one of the more prominent early ones and it is also interesting to note that Unity3D games run on the same underlying framework (mono) http://unity3d.com/showcase/gallery

I note that you didn't provide an example.

He did--he called out Rdio (http://rdio.com) as an example.

Presumably that is the only one. Xamarin features it, but everything else they feature is an in-house corporate line of business app. If there are 'lots of great apps' out there, you'd think they'd tell us.

Not encouraging.

Well, right now I have just built two "in-house corporate line of business apps" and so far, the pay was reasonable and time-savings due to underlying framework huge :)

That's fine - the point is that in those cases the end-user is not the customer, so cost-savings trump user-experience.

There are some case studies here: http://xamarin.com/customers

Screw C#. Xamarin's party trick is F#. It's basically Swift, on steroids, which lets you write a single codebase to target Android, iOS and Windows Phone.

Has anyone actually done this?

Yes. I don't know of any big apps like Rdio that you would recognize yet, because Xamarin hasn't supported F# that long, but there are cross-platform apps being written in F# now.

Actual consumer apps, or in-house line of business apps for corporations?

I believe Tachyus (http://tachyus.com) is using Xamarin + F# for their product.

So, no. Not a consumer app.

"...F#. It's basically Swift..." - that slow after compilation???