The fact that this extensions resizes the thumbnails for you and gives you a number of customisable options is great.
Excellent support too. I highly recommend it. The only drawback is there appears to be some incompatibility with displaying albums within a page Joomblog. It worked fine initially but fell over after upgrades (upgraded both - so not sure where the issue was introduced).
I've only given it a three-star rating because the category function has not been thought out well. You can display testimonials for a particular category which is what you would expect. But if you add a testimonial or click on the read more option, the extension takes you to a page that includes all testimonials, not just the ones related to the category - so this requires support to get it working as you want it to.
I also found that it did not work with breadcrumbs - again I think this will be resolved with support (or switching off breadcrumbs for affected pages) but I would expect it to work without support.