I am attempting the same thing. Here's my scenario:
SQL 2005, 32bit, Win2k3, 1.5 TB DB
In my Test environment, using a copy of my 1.5 TB production database, I am running a DBCC Shrinkfile with the Emptyfile option on a data file that I want to remove to reclaim 60 GB of space. My "hope" was that this operation would complete in a reasonable amount of time and that I could repeat this on four other 60 GB data files. Sadly, after more than ten hours, the first DBCC Shrinkfile command is STILL running.