I'm curious about your concatenation technique. Dynamically creating multiple script objects (with document.createElement) from a data file and injecting them has been reasonably robust for me but I'm not writing a framework so I have far fewer test cases! :-)
Cappuccino has a completely custom loader and concatenated file format that creates a file system representation, such that when you do something akin to XHR("something/blah") it knows that it already downloaded it and gives it to you without a request, that way whether you ship concatenated code or not the code that fetches it is the same.
