I have implemented (in test) a 2003 environment and then introduces a 2010 env to be in co-existance for a while. I can't get any of the PF's to replicate over and can't see the 2003 PF's from the 2010 PF tool. I have mailflow bidirectional with no issues... I have run the basic scripts in the MS outlines for accomplishing the replication and updating the hierarchy.
Exchange 2010 SP1 rollup 2 on win 2008R2
Exchange 2003 SP2 on Win 2003 R2 SP2