What did Shakespeare's plays really sound like back in the day?

Tea at Trianon has a blog post on just that topic, available here. When I was in high school, long ago and far away, my drama/theatre arts teacher mentioned that it was then standard theory that English is Shakespeare's day was spoken much faster than it is now. The thinking went that what is for us a four-hour performance was for Shakespeare and his contemporaries about an hour and a half.