I suspect OKC can make much more accurate predictions than this site, as they have vastly more data (some users answer thousands of questions, most users who are active for more than a few months have answered a couple hundred), vastly more users to compare, and they are pretty savvy about statistical analysis (reading their old blog posts is quite educational on the subject).

But, even given all that data...I find about half of my 99% matches (of which I've talked to maybe a half dozen and gone on a date with maybe four) aren't particularly compatible or interesting, to me. There seem to be other factors at play that just aren't measurable. And, heck, maybe being just like someone else isn't what makes an ideal friend/lover/partner.