My guess is that when you get into the Escient, Request, Kalediscape stuff it is more you are buying the software that these companies sell. Which limits you to what you can do. Thats why I am considering either building my own or getting a music vault that will run the Squeeze software or iTunes, both which offer excellent interfaces, multiple room capability and commonality.
Other than that, I can't see any real reason to get a prepared box with proprietary software as it will pidgeon-hole you.
Other than that, I can't see any real reason to get a prepared box with proprietary software as it will pidgeon-hole you.