I agree with earlier reviews, the game adds some stuff and it's a good expansion. That being said I would like to expound a little bit. First FF has added new cards, replacing the entrance with four entrance cards. This is kind of silly, but on the whole it makes more sense and does indeed fit the box better. Also it allows for certain events like closing one entrance card. Secondly they added some new items and allies and at least one new spell and then made everything more readily available. For instance the new Adventure cards might still extract a heavy toll if one fails they provide more loot than the base game ever did. I would say three or four times more. Also other world cards no longer add doom tokens upon completion, one even takes one doom token off.
Probably the biggest stated difference was the inclusion of blessed and cursed dice. I want more. Think one use, that's it. In my case I rolled the white die once the entire game. They are just green dice but black and white. I wanted something like five terror and a "you lose the game" side and five wilds and a "free common item" for the other. Instead I got a mindless addition.
The true masterpiece of this game is the mythos cards. I like having choices, some are easy, some are hard, they will try to kill and they are fun.
Also of note is the inclusion of additional characters. They have abilities that we like and enjoy. I tried something new and it hurt me while my co-player/girlfriend grabbed the good characters from previous romps through the museum. Additionally the new monsters are interesting, a few give items and then are returned to the cup, one actually nearly kills you. The ancient ones are likewise good but easier than the base game.
In conclusion this expansion adds some things but BGG has forums already suggesting ways to make it harder, if that's any indication. Honestly what I liked about it is that the game is easier, I have items, I have abilities, I do not necessarily need to fear for my life. That being said, this is Lovecraft and Cluthulu, and in many ways I want to play the game on the cover of the box, running from a creature with huge fangs, instead I feel like I played Candyland. I remember from my base games rolling one die and our whole night resting upon the face of that one die. Those were great memories. Out of items, out of time, one roll. This expansion is good, but some things will need to be adjusted accordingly. You won't really bother with the new dice unless a card tells you to, which might never happen. I would say that the price is right, that the added characters and mythos cards and adventure cards are worth the cost, but its not a must-have expansion and it wont make your whole team yell in the mall and almost get you removed. That being said enter the expanded museum at your own risk...