I have always had issues with the Quora "more" button at the bottom - it gets stuck in an endless loop. The rest seems stable and responsive, but that issue alone (over multiple computers and browsers) has made me not bother with Quora.
The native version is mostly UIWebViews embedded within a tab bar controller showing the mobile web app.
If I hadn't had it explicitly pointed out to me that the app is a bunch of web views, I would have thought it was a ton of Core Text drawing going on behind the scenes.
This is actually just wrong. Compare them side by side and you'll see that the web view components in the iPhone app have been specially designed and constructed for the app.