Rated 5 out of 5 stars

If you see navigation bar becomes bigger and smaller when you use SearchWP create a rule in Stylish or use userChrome.css:

@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);

#searchbar .searchbox-tokens-layer,
#searchbar .searchbox-embedded-actions-layer {
margin-top: 0 !important;
margin-bottom: -2px !important;
}

This review is for a previous version of the add-on (2.4.2).  This user has 2 previous reviews of this add-on.