Too much... stuff. Lots of small buttons IN ALL CAPS. Irritating UI "helpfulness" like (just one example) overriding right-click on article titles, so you have to right-click, aim pointer, left-click to open the original in a new tab.
The showstopper for me is the lack of infinite scrolling, although only today (after using NewsBlur for several months!) did I realize it's apparently intentionally crippled so I'd go upgrade to the premium version.
Think that's it. I just looked at Yoleo Reader (https://yoleoreader.com/) and realized that the clean look of that is exactly what I want/need, and what I miss with NewsBlur.
I got a premium NewsBlur account primarily because it was the only non-google reader with good keyboard support. And I kind of like the attempt to add social and commenting features.
But I might move away if I can get a cleaner UI with full google reader-style keyboard support.
This problem could be solved with a 'minimal' skin, perhaps?