By the way, the reason I break the constrains before unparenting is because I discovered that if I unparent objects that have a constraint on them, sometimes they shift position.
You can stop that by doing using the "preserve position" option when you unparent them.
As far as deleting the constraints you will probably need to write a script that will grab all of the constraints in the scene and then find any unconnected ones and bin them. Shouldn't be too hard try using lictConnections on the constraints.
Alan
Technical Director - Framestore
Currently working on: Your Highness
IMDB