One thing that stands out to me is how complete the Keep feels while testing. Sure, there are a few things that are not final, but running across them is actually a surprise sometimes. It's funny when it feels like you're testing a complete and solid product, then see something that brings you up short - "oh yeah, we're still in beta!" It's fun.. with the occasional reminder that it's still not a "final" product, even though it feels like one.

One thing I like is that the ability to give feedback is simple - there's no need to jump through hoops to reach someone. They've made it easy to either report a bug or just send some feedback, and that's a treat.