This is a great plugin. Not seeing any errors in my server log from it and the floater is smooth.
Having an issue where it loads over featured image but that is one of those things a plugin author can't get right every single time for every user because it depends on the theme plus other plugins. When it loads in the correct position, it looks fantastic.
See what I mean here...
I would have done 5 stars but I feel this plugin could go further. There would be a premium edition and more support. There could be more options for fixed buttons and clearer instructions with easier functions for applying them to themes.