What do you like best?
Janrain has several solutions, but in general the idea is to provide a tool for customer identity management.
The fact that they allow to authenticate from all the major social networks and email services and that allow you as a developer to capture relevant data to perform the authentication is a major plus.
You can allow any new or existing user from your website to authenticate from a social network like Facebook, Twitter, or even GMail is great because how many of us has forgotten a password to a website, but you will always have your email or social network opened.
Not only that but the metrics that it shows are very useful, and those allow you to take decisions.
What do you dislike?
Regarding the customer data feature, the profile data storage you would expect to be more flexible but it isn't. That's one thing that I don't like but it doesn't make it a bad tool after all since it has lot's of benefits.
There's also the fact that the idea is to develop less than having custom apps for each social network, but in the end, for providers like Facebook, Twitter, GMail, you have to create a basic app on their side and know how to pass that data to Janrain, but isn't that much extra work.
Recommendations to others considering the product
You have to have strong skills on scalability, web integration and some knowledge on how to create basic social media apps if you want to integrate with some of those.
What business problems are you solving with the product? What benefits have you realized?
I have used it a couple of times with large clients that require to allow new or existing users to authenticate in a website with a social network button or with a mail provider button.
You can either have one custom app for each social network or email provider, or have a cloud based solution that supports most of them.