Thanks for the followup. I got a lot of great responses to this, including the one that pointed to the fact the SSRS scripter tool was rolled up into a larger project. Go figure!
I've used this before and it is the closest thing I know of to 'easily' merge and migrate SSRS instances. As much as Microsoft pushes SSRS as an enterprise reporting tool (and it is pretty good at that creating, serving reports), it is awful from a management perspective. I hope they improve that part of it moving forward. It should be easier to merge, split, migrate, and move an SSRS instance. However, I have heard ramblings that perhaps SSRS is going the way of the dinos...but no official confirmation!