No sound is the biggest issue.
? UI lag is still present.
? Populating lists after launching the app takes a while.
? Video playback is abysmal. Quality doesn't matter. 240p, 360p, 480p videos stutter. 720p plays via slideshow. Note that never have I faced any problems with video playback on my phone. Ever. The first time i watched Hobbit: The Desolation of Smaug was on my phone. 720p H.264 MKV file. They seriously need to fix this sh!t.
? Why doesn't a video automatically switch to landscape mode based on its aspect ratio? Why do I need to unlock the screen rotation for that to happen? Why?
L520 WP8.1.1 with Cyan. On Dev Preview.