I've been using Memberful for several years now. One of the things I like about them most is that they're focused on constantly making the service better without constantly adding new features and making it bloated and difficult to use. I use Memberful for my Homeowners Association (HOA) site where all members are free (yes, Memberful supports that!). I also use it for a membership site that requires a subscription to access premium content. It works perfectly for my needs and it's easy to use shortcodes and functions. For example, I use functions on template pages to show and hide certain information depending on if they're logged in or not, and also what level of membership they have. Additionally, it fully integrates with Discourse, which is what I use for my forum. I love this service!