<p>Mythtv isn't and never was designed to be used for livetv. The function is there because people demanded it but most users on this list and the devs don't use it. Mythtv is designed that you schedule everything and watch it from a recording.</p>
<p>As not many people use it, and none of the devs are particulalry interested channel changing speed hasn't been optimised and so is slow.</p>