I usually use XBMC on a PC hooked up to the TV with HDMI, usually for streaming or local TV shows.
But with the lull over the summer, I'm popping in a few DVDs from the library.
My first impression with XBMC playing DVDs was
'Great, a new menu option just appeared to watch DVDs'
and my second impression was
'This is so slow and choppy it's unwatchable'.
After some internets searching I stumbled across this XBMC forum.
And the solution of changing the audio settings also worked for me.
I had Audio Output set at HDMI and it needed to be Analog.
I did also set the Audio output device to WASAPI - HDMI.
All was well with the world again.
Well other than the fact that I ended up playing DVDs on the PC because the DVD player is only pushing sound and not video.