For me it’s a bit overkill so I’m not sure it would ever be five-star for my current requirements (I was close to giving 5 though). I know it sounds odd but I found the wealth of options and settings a little frustrating when all I wanted to do was display a single testimonial on a page.
Something that might be helpful is the inclusion of everything you have listed under “Shortcode and Widget Options” on this page http://wordpress.org/plugins/testimonials-widget/, maybe on the Example Shortcodes page within WP Admin. It’s a bit frustrating having to go the WordPress.org site to find that info. Including help etc. in the plugin would be useful, maybe links to the FAQ etc (I know you have a link right at the footer but make it more prominent).
Also, the Settings area could do with a facelift/rejig. I find that it’s a bit heavy on whitespace meaning there is lots of scrolling to find settings. You could maybe have a tab in settings that have the “eg shortcodes” and “Shortcode and Widget Options” rather than having it as a seperate link in the sidebar.
Anyway, those are just my thoughts. It’s really more about the usability rather than the functionality.
Have a good weekend!