Its the worst mostly when the shows are not actual HD the ones that are stretched. I believe it has to do with how they simulate the normal sound into 5.1.
The easiest way for you to test for a delay would be connect the cable directly to your tv (don't use the box) use the audio out on your tv and turn up the tv speakers if the sound from the receiver and tv speakers don't line up (echo) the receiver is adding a delay to the sound.
If you get a delay connecting and using things like musical instruments or microphones to it is out of the question. Also if your susceptible to delays you may notice it watching DVD's as well which I was with the 805.