No, I have not. In fact, I was so ignorant that I thought the "media player" application that comes loaded on the tablet was mplayer. When I read posts here, I thought people mentioning mplayer were referring to this pre-installed app. Wow, I was confused.
Do I need to also install mplayer-plugin from Extras? EDIT: mytube is working now. I didn't even have to change any settings. Just installed mplayer. What is the mplayer-plugin from Extras needed for?