Its really easy to implement and to customize, we chose this one because you can customize the like button and replace it with an image. very satisfied so far (:
This app is far more than just a simple like button. Depending on which plan you choose (I'd suggest going with an annual or pay once plan) you have the option to create unlimited button types (one plugin, unlimited widgets) on your pages that you can customize any way you like. Customize icons, text, font, tooltips, and pop-up links. Create "Donate" buttons or other calls-to-action, this is pretty much an "all-in-one" button for whatever you like and on certain plans will allow you to view statistics and votes graph of the plugin. You can see it in action on our website (we use it with the awesome Spruli Loyalty Program app).
We just installed this app today. It took us about 5 minutes to setup our options, and then copy the small code to our Product Snippet. When then tested it on several browsers and on mobile, and it worked and looked nice (we added some css code to center it). We choose the big green and red hands (we wish there was an option for a medium size). In the back-end, this app appears to be far better than other 'Like' apps in the store. It is nicely designed, and there are graphs showing the status of each product voted on. For the back-end, there are several graphical export options, but I did not see an option to export the data as a text file or a spreadsheet. That would be nice, even if it was only available for the paid versions (we're paying for the highest package). Even without the stuff we wish it had, it is much better than the other ones we tested.
The reason we have been looking for something like this is because it will help us get quick and unsolicited feedback from current or potential customers regarding how they like our products. This in turn will assist us in improving our offerings and designs.