I had to use this for the sites in category web part since I had to place two on the same page with different filtervalues for the same field. The way to do this is to find the filtervalue parameter binding entry and add an extra property called "DefaultValue" set this to the proper value and voila.
I hope this saves you some time when you are trying to perform the same task.
If you have any tips, tricks, resources you would like to share with the group please post them as comments or email them to Susan Fischer at susan@clinchportal.com and we will post them in an article.