http://tkf.github.io/2013/06/04/Emacs-is-dead.html
The lack of multi-threading is #1 on his list, and it seems to me for good reason. If one of my emacs buffers locks up (which can happen for any number of reasons), the whole session is hosed.
Notwithstanding that, one thing I'd love to see is an FTP client mode something like FileZilla.