This is really hard to narrow down, because there are so many great features. If you are looking for am amazing HTML5 eBook creator and the ability to showcase, consolidate, and organize all of your content, Uberflip is the best. With no coding skills required, we have made our resources area an eye catching, content rich, interactive library that's easy to update and keep fresh.
My favorite features are:
Ability to add embedded videos directly into the eBooks and giving users control of all types of options within the eBook such as sharing, downloading specific pages, and playing videos.
For the hub: The total flexibility and look and feel of the hub. I've created custom streams, chosen the color scheme, I can easily hide and/or display streams and individual pieces of content, and add additional information to eBooks and video pages.
We had disparate areas in which we housed our content, which isn't necessarily a bad thing, but the Hub allows us to bring in all of our content in one place, share to and from and keep cross domain traffic within the CodeBaby umbrella so to speak. We've seen over double the number of traffic hits on our Hub than on our former standalone blog.