I am a believer in the Predictive Index; it's still the only one I have tried, so I can't comment on the rest, though I hear there are plenty others out there. I think the tool has made our business better and our people happier and more productive; since making these things happen is my job, I am grateful it exists.
"What does it mean for me?" That's it. Whether you're merging companies, making a platform investment or creating a new team through a re-organization, all anyone ever cares about first is what it means for them. Once that question is answered, individuals can focus their hearts and minds on the new team imperative.