Another bookmark for myself and an FYI for readers.
You may have missed this post from our excellent DFS\R team's blog.
When the forest functional level is Windows Server 2003 or Windows Server 2003 interim and the ISTG in a site is running Windows Server 2003 with SP1, you can use a site option to turn off automatic site link bridging for KCC operation without hampering the ability of DFS to use Intersite Messaging to calculate the cost matrix. This site option is set by running the command repadmin /siteoptions +W2K3_BRIDGES_REQUIRED.
7/17/09 modified W2K3_BRIDGES_REQUIRED to +W2K3_BRIDGES_REQUIRED
dfs BASL cost