Saw it this weekend.
It wasn't the WORST movie I've seen this year (Matrix Revolutions wins by a landslide) but it was pretty bad.
Eddie Murphy provides his trademark "oh no you di'int" one-liners and offers absolutely nothing inventive or new. You could watch any of his last 10 movies and get the same thing. Marsha Thomason is hot but a terrible actress and doesn't do anything. The kids were annoying and cliched as fvck and should have been thrown into the pits of hell.
Wallace Shawn provides the only worthwhile and mildly humorous performance in the movie, but even so you might as well go watch The Princess Bride instead.
There were about two places in the movie where I or my g/f jumped, and both were for the same reason which quickly got old -- the "suddenly appearing butler" trick.
The plot is so tired and inane it's not even worth critiquing. The special effects were decent but nothing special and not nearly as impressive as PotC. If you're terribly nostalgic for the Haunted Mansion ride itself and want to see the few references to the ride stuck in the movie, but live too far from Anaheim or Orlando, then do yourself a favor and wait till this makes it to network television. It's really not even worth the price of a rental; it's that underwhelming.
Overall, I think it really deserves the 15% rating on Rotten Tomatoes -- not an absolute failure but the plot is more warmed over than the undead that populate it -- who could also probably do a better acting job for less money than the current cast, and it doesn't offer anything truly inventive or fun to make it worth recommendation as either a family flick or a time waster on a Sunday afternoon.
If you want a movie with some thrills and Disney nostalgia, rent PotC.* You'll thank me later.
*Unless you're Electric Amish, in which case you'll probably want to watch Hudson Hawk instead.