Thanks, I fixed my rating. I didn’t realize that posting a “new” review replaces the old one.
I just found out (while researching how to replace the plugin) that according to the developers the plugin is plain broken at the moment, it’s not really supposed to cost any money.
A pity that WP doesn’t allow to edit ratings or reviews. The plugin wasn’t bad, my rating was all about the $0 -> $299 price surprise which might have been caused by a bug in the plugin.
