Regarding if 2 or more levels are necessary, it can easily be solved by introducing a family of annotations. I suggest abandoning the boolean attribute in favor of (something like) @Supported, @NotSupported, @Experimental, etc. You may likely find the need to express individual attributes at each "level" -- which is more expressive than trying to use a single annotation.
And what's good for the goose is good for the gander. It would be nice to make (at least) @Supported officially part of Java so 3rd libraries can use them too in their own documentation. For example, Google does something quite similar with its @Beta annotation. Paul
