It is an open source project. There are a finite amount of resources available to such a project. From the beginning they've made clear that speed was dependent on those resources. As Larry has pointed out, out of the system engineering cheap,good,fast, they didn't really have a choice about cheap, and they preferred to choose good over fast. I for one am very happy with that choice and very grateful to those who dedicated so much to bring Perl 6 to the place it is today.
I've been playing around with the pre-releases and reading about what is coming. I'm excited at the possibilities to come. The release coming on Christmas (THIS Christmas!!!) is simply locking down (for the most part) the language itself, but will still need a lot of work from all of us, the community, the build up the CPAN (and related) ecosystem to make this a truly viable system. I hope to be a part of that effort.