I have been looking for a good site search solution for years. There are some key analytics you want to know about your site search traffic that are not out of the box with Google Analytics and somewhat difficult to custom implement - keywords searched, searches with no results, and the page that the search took place to name a few.
SearchIQ is a great value, the UI is clean and intuitive, and they have been great to work with.
I am giving them five stars since I love this product and they helped me understand the value of the Featured Image in WordPress. I look forward to seeing better analytics.