I'm using RC1 and I find it much more responsive than older udoobuntu releases but I'm experiencing a strange phenomena with imx-hdmi-soc Analog Stereo Out. I use Totem for video and audio reproduction. Whatever format Totem is playing the hdmi audio is laggish until I start an istance of pavucontrol (Volume Control Settings) then the hdmi audio becomes perfectly fluent! wa..? using imx-vt1613 Analog Stereo Output the audio is always perfect. I'm not looking for a fix I was just willing to share this as a confusing fun fact!