With the Blu-ray, there is about 307 identified so far, in a movie that is 124 minutes long. That's about 2.5 changes per minute, or an alteration every 25 seconds of the film!
(of course, not in actuality, just in terms of mathematics--what's interesting is when you look at the spreadsheet of changes I made you can see these huge surges of changes in certain sections and the different levels they peak at, Mos Eisely and the trench run especially since those have huge surges into level 4..it would be interesting to graph actually).