I will have a max of about 30 items in my lists, so I wanted to avoid scrolling just to make the wizard work a little quicker. It’s no big deal though. I just thought there might be a row height property somwhere.
As for the white space, it also isn’t a big problem other than it seems to act different from all other white space in containers. For instance, if I have a table that could show 20 rows, but was populated with only 5 rows, clicking on the white space doesn’t select the last row. Normally, clicking on white space just brings focus to an object, or even closes an object. It just seemed different when I saw it the first time. I’m just being too picky. 
One other thing- working with Colby the other day, we found that the List.selectedIndex property change generates two events instead of one. I ran some more tests, and the only work-around I could find was binding the selectedIndex to a dynamic property and keying off that instead.
All in all, this is a great component. I needed to build a wizard, and I cascaded five of these list components side-by-side, and from the user’s perspective, it looks like a single dropdown menu where they can select different rows in each column, including multi-selections. It reduces clicks substantially, and will work great with a touch screen.