I tried it a few times but got better results using Google with site:news.ycombinator.com so I haven't kept up with what's been happening with SearchYC.
SearchYC used to take points into account, which is at least one advantage over Google. I don't think it had any special access in the current case, though.
It also let you restrict results to top-level submissions, while the common news.ycombinator.com/item url scheme for both submissions and comments makes it hard to keep comments out of Google results.