I have installed the universal ajax live search in one of my portals 100% based in k2. After installing the search box did not work well, then I went to support and they solved inmediately my problem. Now, my site looks more professional and conveys this feeling to the visitor.
If your site is important to you, you have to give him the best, and certainly, a good search box can make the difference between your website and the competence.
I am very satisfied with this extension and would highly recommend them.