No. I can't think of any meaningful way to compute (or even guess) such a number. If you want to know what's already implemented, please consult the Perl 6 compiler feature matrix.
But to stay in the spirit of the original question, "If you've tried it, what are your thougts on Perl 6?", let me tell you that the percentage of what features are implemented isn't really interesting. Suppose I add an obscure feature to the spec and you don't even understand what it does, the fact that the compilers do not implement it will reduce that mythical percentage. But it does in no way impair your Perl 6 experience.