Honestly that Vader/Obi-Wan fight is the one scene in ANH that I would be okay with if they did a CGI-redo to. After 3 prequel movies and all the years of Clone Wars stories - you go 'sheeesh' these guys may as well be two old fogies from a retirement community fighting with broom handles over who gets the last seat in the van for a trip to Wal-Mart.
Even Luke who really had no true Jedi to fight pretty much kicked Vader's ass, even without 'giving into his hate', just had to wear him out - and he wore out in minutes not hours. Look at the running fights Anakin did in the Prequels, he didn't go 'hold up a sec... gotta catch... my breath.'. Granted he didn't have a mechnical suit, but then again... he should have been able to last far longer simply because of the suit, no arms or legs really to get tired, he's being force fed oxygen and probably drugs and pain killers.
While I wouldn't really want to see Vader going all 'Yoda on Crack' and jumping off walls and such, it would have been nice to see him actually looking competant as a fighter and Obi-Wan, while far older and more 'out of the loop', could still hold his own. They could still keep some of the original footage in, just add in some scenes that are shot more from Obi-Wan's back or obscured with the hood/cloak, at least make them look more like competant swordsmen.