Rakudo Star is aimed at "early adopters" of Perl 6. We know that it still has some bugs, it is far slower than it ought to be, and there are some advanced pieces of the Perl 6 language specification that aren't implemented yet. But Rakudo Perl 6 in its current form is also proving to be viable (and fun) for developing applications and exploring a great new language. These "Star" releases are intended to make Perl 6 more widely available to programmers, grow the Perl 6 codebase, and gain additional end-user feedback about the Perl 6 language and Rakudo's implementation of it.
For those interested, here's a recent post about the history of Perl 6 so far, too.