what lithium features do you like best? which ones do you use most in your community? how does it fare with your community?
Would be great to know a bit of background as to what you are looking for specifically. Is it really just a question around getting a list of what things brands/users like about the Lithium product? Lithium has so many products and so many different use cases around them, just getting a list of what folks like the most seems like a missed opportunity. Are you thinking about launching a community? Do you have one already and want to learn how to optimize your setup. Are you looking for best practices.
In any case, one of the strengths of the Lithium product is the community product and it's basic, easy accessible functionality, the community core. Any brand can easily launch a basic community with advanced features, right there out of the box. User management, moderation tools, gamification, metrics/insights and more, it's all there. Basic customization can be done from the administrator console and for advanced customization there is Studio and SDK (Which we often (ab)use ;-) heavily.
We started working with Reach quite recently which has turned our "marketing" campaigning for our support channels and (pro-)active support content around, like 360 degrees.
I can go on for a while but perhaps, if you can share a little more about your community (plans) more folks can chime in with some focused feedback.