The plugin itself deserves 5 stars, but the upgrade (for the Pro version) is so ridiculous and convoluted, I took off a star for that. In fact the upgrade path deserves 2 stars to be knocked off. A pro version of a plugin is supposed to be EASIER, not harder to deal with.
No way to save the settings, manual upgrade required... which wouldn't be that big of a deal, except that you have to DELETE the previous version (which was being used) before WordPress will allow a manual upgrade, because the directory already exists.
So now I have to recreate what I had set-up. I'm not happy. Oh, and when you click "visit plugin Developer's site" it takes you to the site's home page.... with no obvious instructions/menu on what to choose to find download instructions. The "My Account" is hidden (the plugin is sold through a 3rd party). For anyone looking, start with "Support", then you'll be able to find the "My Account"/login link.
And have your license key handy, you will need to put it in again after you upgrade.
If I wasn't so happy with the plugin I wouldn't go through all this. When the plugin is up for renewal (it's an annual license), I may just downgrade to the free version...which works just fine without all these hoops to jump through.