Not off the top of my head; my only reaction when encountering such "apps" is to immediately close the tab. Why should I keep those in memory? To have myself an argument with some other HN reader? Please.

I'd say that a hefty chunk (if not a majority) of "Show HNs" involving Javascript-heavy anything are riddled with bugs, among said bugs being elements moving around as others load. It's just like web pages in the 90's; for every excellent and well-known app, there tend to be several mangled ones.

EDIT: come to think of it, DuckDuckGo (which I otherwise absolutely love) is a good example of what's being referred to; some elements (particularly for instant answers and "sponsored" results) take longer to load than the search results, and I've found myself frequently clicking the wrong link because of my intended link shifting down without warning. This was especially prevalent prior to the recent redesign (nowadays it seems to be less of a problem).

While maybe this doesn't fit your definition of "web app", it's still relatively JS-heavy by default (though DDG is also an excellent example of progressive enhancement / graceful degradation) and is a decent demonstration of web-app-like concepts (and, in my belief, fits the actual definition of "interactive web app" quite well).