I'm right in saying that Bontrager changed the size of their steerers so that they're more "conventional", I have a 2002 Trek 5500 and would love this new fork...but it won't fit, right?

Trek used to use a 1.25 inch steerer on the lover part of their forks, the upper was 1.125 (standard) this meant that there had to be special tapering forks and that the lower cup of the headset was epoxied into the frame...on the 5900. I'm certain that it was only the 5900, so if you have a 5500 you can use any fork you want.