This 'error' is almost as petty and insignificant as the 'tip of the spear' fiasco from The Avengers. Lets be honest. It's so minute it makes no difference.
Maybe not to a casual viewer, but it most certainly does to a bigger fan - and most certainly to someone more interested in the art of animation. Disney boards have petitions going already, and many people have cancelled their orders due to it. I'd personally argue that it's a MUCH bigger error than the Avengers example. Plus, with the Avengers it was something done on purpose. This on the other hand is just a mistake.
How about the animator that spent days animating the lip sync of "wish I could be" only to have the shots swapped so we see Ariel nonsensically moving her mouth to no words?
To make it clear, the shot near the end where she floats to the bottom of her grotto SHOULD line up with the line "wish I could be..." Then we see Flounder before it cuts to the close up of Ariel for "part of that world." In the new restoration we instead see Flounder for "wish I could be", then Ariel moving her mouth during the pause before "part of that world."
The Lion King error can be seen here:
http://www.youtube.com/watch?v=IWiRPAb8KNw In the Diamond Edition, the clouds that make up Mufasa's ghost have disappeared in the shot where Simba is chasing after him saying "no, please don't leave me". Without the clouds there, it looks like Simba is chasing after... nothing. They never issued a replacement disc, unfortunately.
Both cases of "does it really matter?" In the long run, no - it doesn't make any big difference. But the fact that it's simply a technical mistake - someone literally pressed (or didn't press) the wrong button - means to me that it should be fixed. I assume they both will be for their next release anyways, so there's that to look forward to.