This plugin is ok, however:
1) It does not use search.php to display output, but has built in stuff (unlike his previous plugin, the non-ajax one)
2) When you choose an option and hit search, that option stays chosen, and you are forced to choose something else instead of the form resetting itself (I asked him how to do this and he told me to change JS. I guess he doesn't see a need to have this option in the backend, or at least add a reset button).
3) No filter for numbers / prices. There is an addon available for purchase, but it has only range slider and not FROM and TO textboxes for manual input, and works only with the ajax version, not the other one.
Too bad, could've been perfect. I'll personally stick to the previous version, though this one may be enough for some.