Re: Are there any apps I'm likely to use or have heard of using this?
I agree that x-platform tools which produce apps which don't look or behave like native apps will be rejected - that's why I use Xamarin.
Xamarin produces native look and feel, and native performance, apps. You can't tell the difference as a user between a Xamarin app and a native app.
For some apps built with Xamarin, visit https://xamarin.com/customers/ - of course, Xamarin would only be showing off the nice-looking and successful apps in the case study on this page, so even I take the content there with a pinch of salt!
Regarding pricing - I agree that it prices out smaller companies and 'hobbyists' (I hate that phrase). However, if you're producing commercial software, then the cost should be outweighed by the earnings /benefits from the toolset.