I am using:
Filter by: unread articles
With beta 11 I have no problems scrolling windows with tons of articles in any feed. All pictures, text, etc is already there and viewable, immediatley.
With versions later than beta 11, i.e. beta 12, 13, 14 in particular, each rss article is loaded while I am scrolling thru a feed, images are loaded, boxes are resized, and articles are displayed after a long time of rendering. Very often I have to scroll back and forward to make an article render properly. So in my experience unified layout is broken since version 3 beta 12.
I downgraded to version 3 beta 11.
Hopefully, you'll fix this.