Reading some of these reviews makes me ponder. If you're not a developer or don't understand how browsers work, this might not be a good plugin for you to start with. The concepts are advanced, the options thorough and the level of intelligence to execute them all effectively is pretty high. If it's too complicated you can hire the developers group to fine tune it. Sometimes it does pay to hire competence. :)
I run this on a number of client sites. On rare occasion there are issues but with some time and troubleshooting you can work through them. This plugin has a lot of options, yes, they are good to have. Flexibility per server is a great thing. Every environment is different.
The complexity has grown in the last few years that a UX overhaul is needed. It's time to refactor some of these decisions into something a little cleaner.
The new addition of ad/subscribe/referrals is a bit jarring especially since its on the main plugin landing page for your site--however its easy enough to bypass and not in your way. It's also not quite clear what you get for upgrading the plugin, or is it useable on other properties. Clean up of the marketing message is essential.
So take the reviews with a grain of sand. If you know what you are doing you'll probably be pleased. If you don't, don't complain about not knowing enough to get yourself out of trouble.