I went to a BB in suburban Chicago last year and got in (a long) line at around 4:00. Doors opened at 5:00, but we didn't get in the door untill just about 6:00 AM. The hotest items were gone, of course, but I still got a number of items of interest (including 2 smaller LCD TVs) and some DVDs that were "doorbusters." Some people were still in line after me, probably until about 6:30 AM, so I would say 6:30 to 7:00 AM. Check out lines were quite long, but actually moved rather smoothly/quickly.