I just upgraded to iOS app 1.2.1. While I like the feature enhancements, I find that it is unusable.
On a couple of occasions, an action such as upvoting raised a dialog box saying that the network was unavailable, on which I had to click Retry — and then it succeeded. I doubt that there was a problem with my local network at the time of these errors.
The showstopper, though, is that the UI often becomes completely unresponsive while viewing the Feed: neither tapping nor scrolling does anything. At that point, I can either kill the app or wait a long time and hope that it recovers.
I'm using iOS 8.1.1 on an iPhone 5S.