I haven't had much to do with the 1.6 release and am still using 1.5.4. (Actually, in fact, probably 1.5.3). I don't care which manual is online as long as I can get to the 1.5.4 manual without too much hassle.
But my question has more to do with the 1.6 documentation itself. From following the discussion threads it seems that while a few things may break in 1.5.4 build scripts, there are whole new possibilities to do things elegantly in 1.6 that could only be done in a kludgey fashion in 1.5. My impression is that it's sort of like Java 1.2. When it came out you could still write Java 1.1 code with 1.2, but unless you were aiming for backward compatibility, why would you want to? In other words, I'm looking for a migration guide that shows off the 1.6 way of doing things against the 1.5 way wherever the 1.6 way is more powerful, not just the list of new features that is in the release notes. Is someone working on such documentation? I think it would be valuable.