1. The output for the form is not condusive to specific site styling. embeding the inputs in tables and then hard coding the styles make it impossible to change the look without editing the plugin file thus breaking it for future updates.
2. make it possible to use as a shortcode. it is already available as a widget, so make a short available too.
3. back to hard coding styles, the search results are impossible to style as well. colors and widths should not be a part of the php file. just add classes and IDs so people can adapt it to their own site.