I've been using Patchstack (although I still from time to time say WebARX out of old habit) for roughly 2,5 years. It's a solid product that "just works". For me personally, one thing I really appreciate is how fast they notify you if you're using a plugin with a security issue.
Due to my work, I keep a close eye on certain forums (mostly invite only) to discover any security issues that affect me or my clients. When I compared to the forums I'm in, Patchstack is usually very( ! ) fast to notify their users about security issues.
The service keeps getting updates regularly. @oliversild (which is the only one of the ?makers I've had any contact with, although it was when I was new to the product, is friendly, helpful, and dedicated!
I recommend all WP users to check Patchstack out! :-)