Great plugin!

I love this search bar.

I have implemented on a site I’m working on, here.

Here is some feedback:

Remove the placeholder on click.
I removed mine with the css:

#wpls--input:focus::-webkit-input-placeholder  {color:transparent;}
#wpls--input:focus::-moz-placeholder   {color:transparent;}
#wpls--input:-moz-placeholder   {color:transparent;}

It would also be nice if clicking outside of the search results closed the list.
Lastly, keep the clear results button there when you get no results.

??