Usability 
Newsvibe (image above, right) uses a responsive design which unfortunately seems to work better on PCs than phones. The login form is truncated and unusable work in portrait orientation in the Android browser. You have to switch to landscape to log in and then pages don't reflow properly when switching back to portrait. Another annoyance in the Amdroid browser is that pages are formatted slightly wider than the screen making them tend to skew sideways when scrolling.
But the biggest misfeature of Newsvibe is that it only displays excerpts of items even if the feed contains the item's full text. That forces you to click through to the source site to read the rest wasting time and bandwidth . Newsvibe also seems slower than other readers to pickup new items.
Newsvibe doesn't work in Opera Mini (the log in form is missing).