Carcassonne: Abbey & Mayor

The new abbey tiles are good for filling in holes, and the other new tiles have some interesting features (tunnels, different road orientations and types). The new figures are good if you put a lot of emphasis on farmers in your games. But, if not, they're pretty irrelevant.

A solid pick once you already own the essential first two expansions and are looking for more

The barn - by far the best component. The way it changes the farm game is very interesting.

Mayor - interesting, but ultimately not that useful. It won me one city worth 12 points in a 300 point game.

Wagon - very uninteresting. It requires too much forethought to gain anything out of it.

Nice new tiles. The Abbey tiles generally end up being overpowered or useless though.