I installed your “Testimonials Manager” on my site http://www.puertoricobygps.com and it works like a charm.
However, there's one thing that you should improve. On the "Add New Testimonial" form there should be a drop down menu, right next to the URL field, allowing me to decide if I want that URL to open on the same page or on a new page. That way it would not lead visitors away from my site.
Maybe you could include this little detail in your next revision.
Other than that the plugin is simple, clean and very nice!!!
I love it.