The search bar is pretty fast for me but the problem with the native search engine of Bitcointalk is that it won't work the way we want it to work. But, I have been using the search bar myself for a long time do search for things that I know the search function of the forum will find without any doubt. I recommend you to use Google search engine to search for threads in the website because it'll be a pain in head to do that with the internal search engine of the forum.