UPDATE: I gave up on this approach and moved back to Eclipse Europa 3.3

Much to my dismay, there were just too many bugs trying to get FB to support 3.5 correctly. I had it mostly working, but there are unresolved issues with the ProblemManager Class that caused consistent "internal build error" messages and generally completely unacceptable error reporting.

I don't know about you but the scope of my Flex work is such that I need top-notch error-reporting. And I really don't like having to apply multiple patches to get my IDE to a half-functional state.