I've been using other WordPress plugin to serve live results on my site since a long time, but all of those plugins were just okay, and delivers really slow results.
Just five days back, I decided to test this plugin on my local WordPress server, and after a little tricky installation (messed up a little with using theme's search box id) it worked really well. I didn't expected the search results were so fast and highly relevant. At the same time, I was surprised with the customization level of the plugin, once it's installed you can configure everything on how you wanted the search results to display and from what custom posts or taxonomy, you wanted the plugin to show results. I am now already a fan of this plugin and using it on one of my site with a monthly traffic of 1.5M+ pageviews. All I can say I am highly highly impressed.
Still this plugin has got a lot of room to work on improvement department, as sometimes the results are slow and sometimes it also deliver "no results found" for an already available content, but again when you do the second search for the same search query it perfectly displays the results.
Anyways, thanks a lot for this wonderful plugin! :)