A few points :
1). You only get 1 Obstacle counter in the entire game, use it wisely!
2). The object is to visit DIFFERENT (or unique) cities. It seems obvious in retrospect, but several of us set up little routes in the south where we would zoom around visiting the same cities we visited the previous round. We made a single word change to the objective, adding DIFFERENT to the description.
3). All transportation counters are cleared off the board at the end of each round. We had 2 players who set up routes for future rounds only to see their counters disappear.
That's it! Thanks.