I actually like the change, but I do have two gripes with it:
1. They could've used a better shot of Hayden. The whole looking down at shoes thing was a bit strange
2. For consistency sake, maybe put Ewan in as well. Or on a second thought if its the whole ghost manifesting as the spirit's prime-of-life thing I guess it wouldn't make sense to put Ewan in since Obi-Wan never turned dark.
I saw the version with Shaw first and foremost but it always took me out of the scene that this baby boomer looking guy was the guy behind the Vader mask.
All in all it was necessary IMO to give better linkage with the PT.