And the only one they win the Cup in, I think (happy now, Camilla? )

Harry continues his insane track record of winning basically every game he's not incapacitated in, and I think this is the only book in which all three the Quidditch games are both played and given some significant screen time. Smart move by Rowling to have the tournament end long before the climax of the book, though, as it would have gotten in the way later on.

Like with many other things in these early books, I wonder how much Rowling had planned ahead, and how much she just fit her plotlines in later books around previously established things (this is especially important for the relation between books two and six, I'd say). In this case, you have to wonder if she knew already that Quidditch would be much plagued the next few years, and so she had to have Harry win the Cup now so it was out of the way? Or perhaps she just did it for Wood.

The game is designed rather well, one has to say, although based on the games we see in the books, catching the Snitch seems to yield too many points, unbalancing things. Only in very rare cases does the team taking the Snitch not win the game. Like in the World Cup, where Krum prevents a massive trouncing that makes one wonder about the lack of competitiveness there seems to be in the international game. Then again, Bulgaria having the Seeker it has, and the Snitch yielding as many points as it does, one can imagine Bulgaria got to the final mostly thanks to Krum, winning most games by taking the Snitch while being fewer than 150 points down. But in general, it's a clever invention: it's exciting, it's original, team sizes are small enough that Rowling can flesh all the players out a bit (though the three girls' development is rather minimal), and perhaps most importantly, there's a lot of potential for spectacular come-from-behind victories or narrow escapes.