Kim,

to be reviewed does not mean to be accepted into boost. There are many libs which have been reviewed, but never become a part of boost. Even if phoenix is going to be accepted into boost, it must become a top level lib. Currently it is not the case. After the review there might be provisions under which the library will be accepted (e.g. more documentation, or modified interface etc.). Currently I see it as implementation detail inside the spirit-framework. And therefore it might change with any release. I think this library is already stable, but it is not part of a boost top-level-libs.

Regards,

Ovanes