I'm using the original Apple Watch Sport with music sync'd and playing from the watch. The issue I'm having is when I use the built-in workout app and switch back and forth between that and the music app the device becomes incredibly slow and unresponsive. It appears to be faster when playing music from the phone instead. Is anyone else finding the same thing with their original watch? I am really disappointed with the speed of the watch in general when using iMessages (loading emoticons / past message history) and loading other apps, so much so that I really only use it now for reading/responding to incoming iMessages.