Our app has a few native ui elements like the top bar, the bottom tabs bar, a quick add control that slides in and out, and Facebook style drawers that expose two other webviews. The rest, however, is done in pure HTML/JS/CSS. Angular.js, in fact.
It runs well on old android devices with 2.2 installed, and runs really well on newer Androids and iOS devices. We take full advantage of the benefits HTML5 provides. Most of the user's important data is cached in localStorage so the app loads very quickly. We use websockets to update the app in realtime without the need to rely on long-polling or native push notifications (which we do still have). We have one stylesheet with zero platform specific hacks thanks to the fact that Android and iOS devices use webkit browsers. And laying out our app's interface in CSS/HTML is much more efficient than doing it twice either programmatically or using nib/xml layouts.
We even use http://www.tidesdk.org for desktop native apps and of course that version runs fantastically. We didn't start out using Angular.js on our main web app, but we are slowly starting to transition our mobile app codebase over to our main web app codebase. At some point we will have the largely the same code running across all major offerings of our product.
Every time one of these splashy articles about a well known company moving away from HTML5 comes out I smile knowing that the FUD it will inevitably create will allow those of us who are benefiting immensely from using HTML5 for mobile to continue to enjoy our productivity advantage.
For those who are curious, our product is http://kona.com and the mobile apps are both available in the store. I'd be interested to hear any feedback about how well the apps perform (my email address is in my profile).