fishmanlee said:

Just curious, why was the new canyon needed again (it looks great BTW)? I missed the explanation of what were the problems in the original shot that are being fixed? continuity errors? or just adding things for heightened realism? (dirt from the TIE lasers etc?)

fishmanlee, while the overall 'canyon' sequence itself has a great momentum to it, the effects are very shoddy-looking in the original movie (and Spec. Edit. still) at that point, compared to the rest of the shots before and afterwards.

Here's a more detailed look at some of the reasons, which you may have missed - http://swrevisited.wordpress.com/2013/11/17/canyon-walls/