The desktop experience (where I use Twitter the most) feels like an afterthought. – The new lightweight icons render poorly on non-retina displays. – The font set (not even sure if this changed) feels really heavy in comparison to the iconography. – The profile card on the top-left falls apart with the circular avatar – There are spacing issues in the "who to follow" card

Overall the page feels really "loose". Maybe the mobile experience is better (high resolution displays and mobile guidelines usually help keep the things I listed above tight on mobile) but I'm pretty disappointed with the result of the desktop site. Didn't feel broken to me before.

edit: I can't get the markdown to work for the list above, sorry.