- search is actually usable now, was completely useless before acquisition
- new messaging features are better than stuff they had before
- rich text editor better than the one they had before (except if you want to edit in HTML or Markdown in which case it completely sucks now, but very few people probably post in HTML or Markdown)
- replies, I have hardly ever seen them used before they were removed. in any case, the new implementation is much better
- should I even mention the freaking video player?
Of course the users will complain, but I mean this is Tumblr, the userbase will complain about everything.