I'll toss my congratulatory two cents into the heap.

After playing a lot of board games, I have to admit that Settlers of Catan offers more variety in gaming outcomes than any other primarily skill-based game I've ever played. While the board layout changes every game, the numbers which are assigned to tiles to make them more or less likely to produce resources (an important quality in this game) are laid down in a very specific way so as to maintain a semblance of order. This means that there is rarely a super space that means an automatic victory for one player. At the same time, the appearance of the barren desert (a finer point of the way the numbers are assigned and an important tile in the game) allows for a small amount of variability. It's really pretty brilliant.

I wouldn't invest in the expansion boxes since I find that they strip the game of its beautiful simplicity and add many scenarios where it is more luck-based. Although, I might buy them in the original German packaging just so I have a cool box that says DIE SIEDLER VON CATAN on it.