new maps? Great! Forum cards? Fun! And I don't care that they may or may not be balanced. They add a bit of zing to the game. Salt? Eh, don't really care about it. Seems to take away some of the fun of struggling with limitations (whereas the forum cards do this as well but at least add zing!).
Lowered rating. Not sure why, but the expansion makes me care less about the game when I play it. I think I prefer the directness of knowing exactly the limitations of each other player, and how the players react to those limitations. With the expansion, it's harder to keep track of special powers and what other players may be planning to do. Thus, I stop caring about what the other players do do.
Also, the expansion does slow the game down about 20%, which doesn't sound like much, but I really like the speedy chugging along of the base game.