I highly recommend moving to phoenix (despite comments made later in this thread). The library is extremely powerful and stable and has been conditionally accepted ( <http://lists.boost.org/boost-announce/2008/10/0205.php> ). The documentation is excellent and the support is speedy. I find phoenix constructs to be far more readable than boost.lambda resulting in overall improved understanding of the code's intent.
Documentation can be found here: <http://www.boost.org/doc/libs/1_42_0/libs/spirit/phoenix/doc/html/index.html>