since the last time I checked (could be they’ve made progress since then):

• subtitle auto sync
• smart collections
• way better support for downloads, particularly transcoded ones
• skip intro and credits
• better UI (this one is subjective but I did find annoying little bugs often)
• I’ve found that it takes way longer to update & scan larger libraries
• overall disparity between clients on different platforms (in my case, webos, firetv and iOS).

in short it’s a lot of tiny little things that make my overall experience just annoying.

because it’s actually usable?

like Crash and Shakespeare in Love?