I was surprised to see all the negative reviews for 6scan. I've been using the service for about a year and I've been very happy with it.
Of course, I knew it was a paid plugin to begin with. I think that's where a lot of people feel cheated because they thought it was a free plugin when they downloaded it and then it probably says you need to upgrade to fix such and such problem.
For me though, it's been a good experience.
Every time I've contacted support for anything, they've always gotten back to me quickly and resolved whatever I was asking about right away, which I would expect from a paid plugin.
I tested out most of the major competitors back when I was building a security strategy. To me 6scan seemed to be a direct competitor of bulletproof security, which I liked a lot as they provide preventative protection instead of just scanning for existing infections.
But 6scan was a lot easier to navigate and a lot more hands off. I really decided to go with them though when they added the login security and backup features. It seemed like it was worth the price to have all those things in one and not have to deal with compatibility issues between the multiple plugins needed to replace 6scan.
One thing I will say though is that it was cheaper when I signed up for the service. It's gotten a bit pricey now, so that's something to consider.