I've always been undecided on the change. On the one hand, I don't know if Luke would recognize Hayden Anakin, and on the other hand it's the Force and showing him being redeemed back to his former self carries a lot of weight. As a change it does its thematic job well enough.
But, I still prefer Shaw.
I would think when you're dealing with an idea as new-agey as the Force and the way Jedi are able to do almost anything just by 'feeling' it and using it that two people with a connection as profound as Luke and Anakin could be expected to be able to recognize each other no matter what they looked like.