This RSmonials works fine, although it has something to be improved. For example, the language file is not complete, so I can not make a full translation. This prevented me from introducing it to more local Joomla users.
By the way, I think the backend testimonials list should be more neat, without showing picture and extra information directly on the list, these info should be displayed on the detail page, not on the list.
Anyway, as a free software, this is an excellent extension for Joomla. I like it.